PZ - Loading Dock Noise Assessment YANTIS
AC@ U ST I C S
COSTCO MERIDIAN LOADING DOCK SOUND
MEASUREMENTS
PREPARED FOR
BARGHAUSEN CONSULTING ENGINEERS
BY
YANTIS ACOUSTICS
MICHAEL R. YANTIS, P.E.
AUGUST 31, 2022
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 2
EXECUTIVE SUMMARY
As part of the Costco's investigation to modify the receiving hours of operation at their
Meridian, Idaho facility, measurements of sound created by delivery trucks and loading dock
activities were made in early July 2022. Measurements were made at two locations, one near
the loading dock and one near the on-site truck route south of the building.
Sound from loading dock activity was the dominant audible source at the measurement
locations early in the morning, but background sound from other sources dominated the
environment the rest of the day.
Measured levels were used to calculate the sound at the closest future residences adjacent to
the Costco site. Sound at the residences is substantially less than the maximum acceptable
residential sound levels per guidelines published by the Department of Housing and Urban
Development (HUD).
Sound from loading dock activities could cause sleep interference inside the bedrooms of the
residential property to the west and south, if the residents have their windows open for
ventilation. However, the single family residences to the west and the apartments to the south
provide air conditioning as standard features. With bedroom windows closed, the interior
sound levels produced by the loading dock activity is less than World Health Organization
guidelines for sleep interference.
INTRODUCTION
As part of the research related to changing the hours of receiving operation, measurements of
sound created by delivery trucks and loading dock activities were made on July 7t" and July 8th
The sources of sound associated with the loading dock are delivery trucks traveling onsite and
maneuvering into the loading dock, unloading sound when the semi-truck trailers are backed
into the loading dock, and forklift operation inside and outside the warehouse.
The loading dock is busiest first thing in the morning. Semi-trucks queue up on the south side of
the warehouse, far from the loading dock, waiting for the time when they are allowed to travel
to the loading dock. While waiting, they idle on the driveway south of the building. All three of
the loading bays are frequently occupied early in the day.
The Costco Warehouse is bordered by commercial and residential property. Residential
property is to the west and south of the site. Multi-family housing was being constructed south
of the site during the measurements. Similarly, high density single family housing was being
constructed west of the Costco site.
A landscape buffer and solid wood fence separate the Costco Warehouse from the adjacent
properties.
DESCRIPTION OF MEASUREMENTS
Measurements were taken at two locations near the property boundary of the Costco site. One
meter was set near the west property boundary, near the loading dock. The other meter was
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 3
set near the south property boundary where loading dock activity was not significant but near
the on-site truck path to the loading dock. Figure 1 shows an aerial photograph of the Costco
site, prior to the start of the residential construction to the west and south. Figures 2 and 3
show photos of the microphone position for each location.
Measurements ran continuously for a 24-hour period. The meters recorded the sound levels
each second and saved the data for later analysis.
- k
N� ■
i'
WI
Loading Dock Location
R
1 �
Truck route on site
South BmOary Location
■ram ,
Figure 1 - Costco Meridian site and truck routes
AS
Microphone ; { _
s
Figure 2 - Microphone location at the west boundary, near the loading dock
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 4
r
All;�
Microphone
"r
Ir
t L
... , ^•::.ram
Figure 3 -Microphone location at the south boundary
The measurement equipment is listed in Table 1.
........ ......... ................................................... ......... ......... .........
Measurement Location Measurement Equipment Serial Number
......................................................................................................................................................................................................................................................................................................................................................:........... ...............................................................
Loading Dock Rion NL 52 Sound Level Meter 764975
hBoundary L i n Ri nNL 2 n Level M r 1 4
; BoutLocation 0 5 SoundMeter 33 83
..............................................................................................................................................................:.........................................................................................................................................................................................:.....................................................................................................
:
Table 1 - Measurement equipment
Loading dock activity was observed from 4:30 a.m. to 10:00 a.m. and sporadically between
10:00 a.m. and 10:00 p.m. It was not observed between 10:00 p.m. and 4:30 a.m. A log of
loading dock activity was taken while onsite and correlated with the time history of the sound
level measurements.
SURROUNDING PROPERTY
The zoning map of the area is shown in Figure 4. Property closest to the loading dock is to the
west and is zoned R-15, residential with 15 residences per acre. Property south of the Costco
site is zoned R-40, residential with 40 residences per acre. Both properties are currently under
development, with high density single family housing being constructed to the west and
apartments being constructed to the south.
A photo of the residential property under construction to the west is shown in Figure 5.
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 5
s+r y VVVQL VI III IUVII L]IVU 7
I r 7 I C _'�Ir
-�--_- ------------------ r
i IRVINE NO 03
Costco Warehouse
B i7i1 JD F
rll o 12
� L I DS
i
-_'—_--- 1RVI YE M1U 01
�r R � N Ten Mile Road
SILVERLEAF
*DGE I
'^ No 01
LRW — - -------
Figure 4—Zoning surrounding the Costco Warehouse site
- d T
rti
Figure S- Residential construction west of the Costco site
SOUND MEASUREMENT METRICS
The human ear responds differently to sounds at different frequencies (pitch). This is
demonstrated by the fact that we hear higher pitched sounds easier than lower ones of the
same magnitude. To compensate for the different loudness as perceived by humans at
different pitches, a standard weighting curve is applied to measured levels. This weighting
curve represents the sensitivity of the human ear and is labeled "A" weighting. The units of
magnitude of the sound are recorded as dBA, or "A"- weighted decibels, which is a logarithmic
scale.
Because the decibel scale is logarithmic, individual dB ratings for different sound sources
cannot be added directly to give the dB sum of the combination of these sources. Two sound
sources producing equal dB ratings at a given location will produce a composite sound that is 3
dB greater than the individual levels. Similarly, the loudness of sounds does not vary
arithmetically. A 3 dB difference in environmental sound levels is normally considered a slight
difference in loudness. A difference of S dB, however, is easily perceptible, and considered
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 6
significant. A 10 dB difference is perceived as half or twice as loud, depending on the relative
levels.
Table 2 presents examples of common sound levels.
SPL dBA Example
0 Threshold of audibility
20 Quiet rural area (no traffic)
40 Suburban neighborhood (distant traffic)
60 Normal conversation
70 Busy freeway
100 Jackhammer
130 Threshold of pain
Table 2 - Examples of common sound levels
The Leq descriptor is the Equivalent Sound Level, which is the dBA level of a constant sound
which has the same acoustical energy as the time-varying sound, described by the
Environmental Protection Agency as the "single value of sound level for any desired duration,
which includes all of the time-varying sound energy in the measurement period". Because of
the logarithmic scale, sounds that are 10 dB higher have ten times the acoustic energy.
Therefore, a source that produces a constant sound level of 60 dBA for a ten minute duration,
and then produces a constant sound level of 70 dBA for ten minutes would produce an Leq of 67
dBA (the logarithmic average of 60 and 70) for the entire 20-minute duration. Note that the
level in the Leq calculation is closer to the higher sound level because the higher level has more
energy.
The Ldn is the Day-Night Equivalent Sound Level, which is the average Leq for a 24-hour period,
with a 10 dB penalty added to sound levels that occur between the hours of 10:00 p.m. and
7:00 a.m. Studies have shown that the Ldn is the metric that correlates most closely with a
person's overall impression of their acoustic environment.
The Lmax sound descriptor is the maximum instantaneous sound (technically, rms or root mean
square) for any given duration of measurement.
SOUND SOURCES
Delivery Trucks
Delivery trucks enter the site from North Ten Mile Road, travel along the driveway south of the
building, turn north at the west side of the building, and then back into the loading dock, if they
are a semi-truck. After unloading, trucks exist the site to the north, onto West Chinden
Boulevard.
Non-semi delivery trucks stop at the west side of the store and unload through roll-up doors in
that face of the building.
Neighborhood sound sources were significant. West Chinden Boulevard is a busy street, and its
sound was significant at the west boundary location from 6:00 a.m. to close to midnight.
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 7
Construction sound from the apartment project to the south was a significant sound source at
the nearby microphone position during daytime hours. Although construction activity occurred
on the single family development west of Costco, it was not a significant contributor to the
sound measurement near the loading dock.
Loading Dock Activity
After the semi-truck is parked at the loading dock, the primary sound sources are:
• Engine idling
• Back-up beepers from the forklifts. Forklifts are busy during unloading, traveling into the
semi-truck and then back into the warehouse to stack the palleted merchandise. During
the measurements, a roll-up door on the west side of the building was open. Back-up
beeper sound emitted from this opening and from open (unoccupied) loading dock bay
doors.
• Impulsive sound ("bangs") radiating from the trailer when the forklift enters and leaves
the truck, created by the small elevation change between the trailer bed and the loading
dock leveler.
Figures 6 and 7 are photographs of the loading dock taken from the north and west,
respectively.
sm1aNi' .Yr
Figure 6- Photo from north of the loading dock
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 8
14
Figure 7- Photo of the loading dock from the west
After the early morning rush, there are occasional semi-truck deliveries throughout the day.
Pallet maintenance occurs west of the loading dock. Pallets are stacked and organized using a
forklift.
MEASUREMENT RESULTS
Measurement results are documented in Figures 8 and 9.
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 9
24 Hour Measurement Near Loading Dock
80
Loading dock activity
A
0 70
E
a
a
9 EO
v
v
a` 50
'o
40
These periods will the minimum
sound levels rise above 50 dBA are
indicative of loading dock activity
30
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vicpo a$mmrv4 3 a8mm"rv'��"on
-- -- ,.rv..i min M'vv�+�mn.onnmmmaavaom - -tiNHM.+m<en vein cbrncowwmm
Time Ihh!mm!ss) ~~~
Figure 8 - Measured 24 hour sound levels (1 second intervals) near loading dock
24 Hour Measurement at South Boundary
Semi-truck passings
by measurement
as
location
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0
a
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JIM
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50
c
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0
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30
Q Q a Q a Q Q a a Q a a Q a Q a Q Q Q a Q Q Q Q Q Q 4
T rN o'vm 'A IN uO1i aIN
maw oiti W mco�$a�+�voM �a a am"i vao PPry V
~ ~~ Time fhh!mm!s5) ~~
Figure 9 - Measured 24 hour sound levels (1 second intervals) at sound boundary
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 0 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 10
CALCULATED EXTERIOR SOUND LEVELS AT ADJACENT PROPERTIES
Sound levels from the loading dock activity were measured on Costco property. The measured
sound levels were used to calculate the sound levels at nearby residential property.
Calculations for Properties to the West
Compared to the west boundary measurement location, residential homes to the west are
further from the loading dock and have an intervening landscape buffer and wood fence. These
factors reduce the sound at the residential receivers compared to what was measured at the
microphone. The microphone was 100 feet from the semi-truck trailer in the loading dock. A
semi-truck trailer parked in the loading dock location was used as the sound source location
because the dominant sounds from the loading dock activity were trucks idling and impulsive
sound radiating from the sides of the trailer when fork-lifts entered and left the trailer. Back-up
beeper sound emitting from the open door of the warehouse near the loading dock was very
close to the same distance from the west property boundary. Trucks traveling to the loading
dock pass slightly closer to the residential property but also closer to the measurement
microphone, so the distance attenuation used for the trailer is still valid.
The development west of Costco is called Cadence at Bainbridge. Although many homes have
been built and are occupied, the homes immediately adjacent to the loading dock were not yet
under construction at the time of the measurement. The closest distance between a truck
parked in the loading dock and the solid wood fence at the west property boundary is 81 feet.
The wood fence sits on an earth berm covered in landscape rock on the Costco side. The berm
continues on the residential side. It was estimated that the back of the homes facing Costco will
be 56 feet from the property line.
Sound is attenuated with distance. The loading dock sound sources are small when compared
with the distance to the residential receivers, and therefore act as a point source. Sound
radiates spherically from a point source and dissipates at a rate of 6 dB per doubling of
distance.
The measurement microphone was located in front of the wood fence. The fence affected the
sound measured from the loading dock as well as that from West Chinden Boulevard.
Reflections from the fence increased the sound from the loading dock at the microphone,
adding 3 dB to the measured sound. Sound from West Chinden Boulevard was also increased
by the presence of the fence, but at the same time, the fence occluded half of the length of the
boulevard from the microphone, decreasing the measured level by the same amount. These
two aspects canceled the fence effect for West Chinden traffic.
When the residential development construction is complete, homes in the development will
block part of the sound from West Chinden Boulevard, for homes near the loading dock.
Although the sound from the loading dock will not be affected, it is expected that overall sound
levels received by homes near the loading dock will be less than documented in this report.
The wood fence at the west property line acts as an acoustic barrier for loading dock sound
received by future residential receivers but does not reduce sound from West Chinden
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 11
Boulevard. The fence is nominally 6 feet tall but slightly taller in some locations. With the 4 foot
earth berm, the fence height above the elevation of the Costco parking lot is 10 feet. Although
there are minor gaps between the fence boards and the fence posts, the bulk of the fence is
airtight and the small gaps do not significantly decrease the effectiveness of the fence.
Barrier attenuation varies with the frequency of the sound. In addition to the overall A-
weighted sound levels, octave band levels were measured to obtain the frequency content of
the sound. The energy average (Leq) octave band sound levels for sound created between the
hours of 5:00 a.m. and 6:00 a.m. were used to determine the barrier attenuation.
Table 3 documents the attenuation factors applied to the loading dock measurements, for
calculated sound levels at the future residence west of the Costco loading dock.
Attenuation Attenuation, dBA
Component
Distance 3
......>......................................................................................................
Barrier 9
.... ..............................................................................................................
Fence reflection 3
:.....................................................................................................:.....................................................................................................:
Total 15
.....................................................................................................
Table 3 -Attenuation factors for residences to the west
The attenuation factors were not applied directly to the measured sound levels to determine
the sound levels at the residences. During much of the day, sound from West Chinden
Boulevard was significant. That sound would be the same at the microphone location and the
residential receivers and would also be the same if the loading dock was not present.
The attenuation factors should only be applied to sound created by the loading dock, not to
neighborhood sound. The traffic sound within the measurement data was estimated by
analyzing the second-by-second data and finding times when the loading dock activity as not
present.
Figure 10 shows example time periods where the sound from traffic was analyzed separately.
During early morning hours, when both the loading dock and W. Chinden Boulevard were busy,
there was not a clear distinction between loading dock activity and traffic sound. During these
times, the background sound without the loading dock activity was estimated by how it varied
with traffic volumes through the rest of the day. Based on this analysis, traffic sound when W.
Chinden Boulevard was active varied from 52 dBA to 56 dBA.
During most of the day, after the morning loading dock busy time, loading dock activity was
occasional, as documented in Figure 10.
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 12
Loading Dock Sound Levels,5:30 p.m.-9:00 p.m.
9r,,-
Traffic Noise
ao.o
a
0 70.0
m
a
m
60.0
E"
a
S 50.0
40.0
30.0
a o n a i n a n o n c a n a a o a a a a s a o n o n n i n i n o a n a a n a a a a i a a n a n n a n o n c a n o
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
i6 i?5avas
w m w m m ro m m m m w m m
Time(hh:mm:ss)
Figure 10- Measured sound levels showing loading dock and background(mostly traffic) sound
Table 4 documents the measured hourly Leq at the west boundary measurement location, the
calculated Leq if all the measured sound was produced by the loading dock, background sound
(mostly sound from W. Chinden Boulevard), and the compiled Leq at the residence, substituting
background sound for the calculated Leq where necessary.
The second column in the table, "Maximum Possible Loading Dock Sound at Residence
(Measured — 15 dB)" typically grossly underpredicts the sound levels at the residential property,
since for most of the day, the loading dock is not the dominant sound source. It assumes,
though, that all the sound measured during that hour was due to the loading dock, and
therefore subtracts the attenuation to the residential property from the measured value.
The fourth column, "Compiled Leq at Residence, dBA" is calculated by logarithmically adding
the maximum possible loading dock sound with the background traffic sound.
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 13
......................................................................................................................................................................, .......................................................................................................................................................................................................
Measured Leq, Maximum Possible Background Sound Compiled Leg
Time West Boundary, Loading Dock Sound at (no loading dock at Residence,
Residence (Measured— i
dBA (Note 1) 15 dB), dBA(Note 2) sound present) dBA
11 a.m. - 12 59 44 52 53
...........................................................................................................................--....................................................................................................................................................................................................................................................................................................................................................................
12- 1 p.m. 52 37 52 52
..............................................--.....................................................................---................................................................................................................................................................................................................................................................................
...................................................................................
.
1-2 p.m. 52 37 52 52
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
2-3 p.m. 53 38 52 52
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
3-4 p.m. 59 44 52 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
4-5 p.m. 54 39 52 52
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
5-6 p.m. 57 42 54 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
6-7 p.m. 56 41 54 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
7-8 p.m. 58 43 53 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
8-9 p.m. 56 41 53 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
9- 10 P.M. 53 38 53 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
10—11 P.M. 58 43 53 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
11 p.m.—12 53 38 53 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
12—1 a.m. 53 38 53 53
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
1—2 a.m. 41 26 41 41
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
2—3 a.m. 40 25 40 40
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
3—4 a.m. 43 28 40 40
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
4—5 a.m. 58 43 44 46
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
5—6 a.m. 60 45 48 50
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
6—7 a.m. 63 48 53 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
7—8 a.m. 61 46 54 55
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
8—9 a.m. 62 47 53 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
9—10 a.m. 60 45 53 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
10—11 a.m. 60 45 53 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Ld n 64 49 57 58
Note 1: Loading dock activity was busiest between the hours of 4:15 a.m. and 9:00 a.m.
Note 2:This column assumes that all the measured sound was due to loading dock activity,which is only the case
during early morning hours.
Table 4 - Calculated sound levels at the residential property to the west
The calculated values in Table 4 are based on a receiver height of 6 feet. This is a valid receiver
height for a person standing near the rear of the future home to the west. It is also valid for
calculating the sound inside the future home, based on exterior windows that extend from 3
feet to 8 feet above the ground level.
The construction of the homes immediately west of Costco had not begun at the time of the
measurements. The residential community is Cadence at Bainbridge, a 55+ community. The
development offers 14 floor plans on their website, 2 of which have upper stories. Homes along
the eastern boundary of the development, bordering the Costco site, will only be single story
homes, according to a representative of the development company for the site.
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 0 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 14
Calculations for Properties to the South
Although there is the same type of wood fence at the south property line, it is not tall enough
to provide attenuation to the upper story apartments from trucks driving on the driveway south
of the Costco building. The difference between measured sound at the south microphone and
that received by the closest apartments is due to distance only. The distance between the truck
path and the nearest apartments is 56 feet, compared to the truck to microphone distance of
22 feet. The resulting distance attenuation is 8 dB.
The sound at the sound properly line included traffic sound from W. Chinden Boulevard and
Ten Mile Road, overhead planes, construction activity at the apartments to the west, and
delivery trucks as they either idle on the driveway south of the building or travel on that
driveway toward the loading dock.
Sound from idling trucks or trucks passing by the microphone are easy to identify in the
measurement history, as shown in Figure 11.
Sound at South Property Line-4 a.m.-6 a.m.
�c
Truck Idling
and Pass-by
so
70
Truck Pass-by
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�➢ h N aQ-•1 ui A Oi O N vi iO W O.-1 m Q iO o0 T •• •• IM1 O� 4 v. 11 W O N ui M m •• •• ➢ 6 �'1 N vi 11 Qi
BooSoo �' � Maa $ aQa4uoN Sea $ eev ..
Time(hh:mm:ss)
Figure 11 - Measured sound at south property line, 4 a.m. - 6 a.m.
Construction activity was significant and will not be present after the apartments are occupied.
Neighborhood background sound was elevated considerably when construction activity was
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 15
present. Figure 12 shows the measured sound levels from 4:00 p.m. to 10:00 p.m. when few
loading dock truck events were present.
Measured Noise at the South Property Line,4:00 p.m.- 10 p,r
75
70 Construction Activity
65
o 60
E
0
v 55
a
a
a
� 50
v
v
s 45
C
O
y
40
35
30
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v v v aev v v v v n v u v —-- -- - - mm rin�rII I W d �e
m�od ofi � oti od ofi
Time(hh:mm:ss)
Figure 12 - Measured sound at the south boundary, 4 p.m. - 10 p.m.
The fence caused a 3 dB increase in measured sound levels at the measurement microphone,
just like it did at the west location. When added to the distance attenuation, the total
attenuation between the microphone and the apartments was 11 dBA.
Table 5 documents the calculated level at the closest apartments south of the Costco site, in
the same manner as Table 4.
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 0 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 16
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Measured Leq, Maximum Possible Background Sound Compiled Leg
Time South Boundary, Loading Dock Sound at (no loading dock at Residence,
Apartments (Measured
dBA (Note 1) _11 dB), dBA (Note 1) sound present) dBA
....................................................................................................
11 a.m. - 12 60 49 60(Note 2) 60
.................................................................................................. .....................................................................................................................................
12- 1 p.m. 51 40 49 49
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
1-2 p.m. 52 41 52 53
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
2-3 p.m. 55 44 55 55
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
3-4 p.m. 56 45 56 56
.......................................................................................................................................................................................................................................
4-5 p.m. 57 46 57 58
.......................................................................................................................................................................................................................................
5-6 p.m. 55 44 55 56
.......................................................................................................................................................................................................................................
6-7 p.m. 47 36 47 47
.......................................................................................................................................................................................................................................
7-8 p.m. 46 32 43 43
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
8-9 p.m. 44 33 44 45
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
9- 10 P.M. 47 36 47 47
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
10—11 P.M. 47 36 47 47
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
11 p.m.—12 43 32 43 43
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
12—1 a.m. 40 29 40 41
...............................................................................................................................................................................................................................................
1—2 a.m. 41 30 41 42
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
2—3 a.m. 39 28 39 40
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
3—4 a.m. 39 28 39 40
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................,
4—5 a.m. 55 44 43 47
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
5—6 a.m. 55 44 41 46
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
6—7 a.m. 56 45 54 54
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
7—8 a.m. 53 42 47 49
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
8—9 a.m. 54 43 50 51
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
9—10 a.m. 52 41 49 49
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
10—11 a.m. 51 49 48 52
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Ldn 58 47 55 56
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Note 1:This would be the sound level at the apartments if all the measured sound were due to truck activity on
the Costco driveway.That is only the case in the early morning hours.
Note 2:The source of sound for this hour is not known.Sound levels are significantly higher than average, but it
does not look like truck delivery activity.
Table 5- Calculated sound levels at the apartments to the south
PERTINENT CRITERIA
The reaction of future residents to the sound created by Costco loading dock activity will vary
with individuals. Some people are more sensitive to sound than others. Hundreds, if not
thousands, of studies have been conducted on the human reaction to sound, correlating
annoyance and adverse health effects to sound.
Section 6-3-6 of the City of Meridian Municipal Code addresses sound as a public nuisance. In
section "A", "Prohibited acts" states that "between the hours of 11:00 p.m. and 6:00 a.m., or at
Michael R. Yantis, P.E., Hon AIA 6 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 17
any time so as to unreasonably disturb or interfere with the peace, comfort or enjoyment of
others, it is unlawful for any person to cause, or for any person in possession of property to
allow to originate from such property, sound that is a public disturbance sound." It goes on to
define sounds that are classified as a public disturbance sound but does not include in that list
any sound sources that would relate to Costco's loading dock.
The State of Idaho does not have regulations that would limit the sound between Costco and its
neighbors.
Federal government agencies have sound guidelines. The Federal Aviation Administration
(FAA), Federal Highway Administration (FHWA) and the Department of Housing and Urban
Development (HUD) all have sound regulations or standards. The sound guidelines are
consistent between agencies. The most applicable guidelines are those by HUD. HUD uses the
Ldn descriptor. Table 6 documents HUD guidelines for residential developments.
Ldn Range, dBA Standard
:............................................................................................................................................................................................................:....................................................................................................................................................:
65 or less Acceptable
Exceeding 65 but not exceeding 75 Normally Unacceptable
Exceeding 75 Unacceptable
............................................................................................................................................................................................................:....................................................................................................................................................:
Table 6- HUD sound guidelines for residential property
The Environmental Protection Agency does not issue sound standards but does publish
research. The seminal document on sound published by the EPA was its "Levels" document,
officially titled "Information on Levels of Environmental Sound Requisite to Protect Public
Health and Welfare with an Adequate Margin of Safety", published in April 1974.
The documents states clearly that it is not a guideline or a standard, because the sound levels
identified in the document do not consider the cost of mitigation. Guidelines from agencies like
HUD have made the effort to find a balance between creating an acceptable sound
environment and the subsequent cost of the associated mitigation.
The Levels document states that an Ldn of 55 dBA outdoors and 45 dBA indoors meet the
criteria for spoken conversation, working, sleeping and other activities "with an adequate
margin of safety". They are typically considered as the "ideal" maximum sound levels for
residential properties, without regard to the practical issues of cost.
Sound levels detrimental to sleep have been a source of study for more than 50 years. It is still
an active research topic in academia. It is complicated, because people can become acclimated
to sounds that regularly occur in their environment, even if the levels are quite high. Research
has shown that even if people become accustomed to sound levels that would typically
interrupt sleep, adverse physiological effects can still occur.
The World Health Organization guidelines and recommendations (1999) include sleep
interference criteria. According to the WHO, average (Leq) sound levels should not exceed 30
dBA during the sleep period and if the maximum sound levels exceed (Lmax)of 45 dBA, sleep
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 0 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 18
interference is likely. More specifically, it recommends that the maximum level of 45 dBA not
be exceed for more than 10— 15 times per night.
CALCULATED INTERIOR SOUND LEVELS AT ADJACENT PROPERTIES
Interior sound levels caused by sound sources external to the home are less than the exterior
sound. Even with windows partially open for ventilation, a reduction in sound occurs. The
amount of reduction for open windows depends primarily on the size of the opening compared
to the size of the exterior wall of the room, but also depends on where someone is listening to
the sound in the room. A reduction of sound of 15 dB is commonly assigned to a partially open
window in environmental sound studies. If someone is standing at or very near the window, the
sound reduction will be less. A conservative sound reduction estimate of 27 dB for an exterior
facade with closed windows is used in this report. It is conservative because it was documented
as part of the 1974 EPA "Levels" document, and thermal efficiency and the corresponding
acoustic reduction have improved since that time.
The residential development west of Costco (Cadence at Bainbridge 55+ Community) and the
apartment buildings to the South (Olivia Apartments) provide air conditioning as a standard
feature.
Interior sound levels were calculated with open and closed windows and for average (Leq) and
maximum (Lmax) sound levels. Table 7 documents the sound levels inside the homes to the
west and apartments to the south.
Average Sound
Maximum Interior Number of Events over
Level, (Leq, Sound Level, dBA 45 dBA
Location
dBA), Windows
Windows Windows Windows Windows
Open Open Closed Open Closed
.........................................................................:.................................................................................................:................................................................:.....................................................................:.........................................................................................................................................
Homes west 27 56 44 26 0
of Costco
............................................................................................................................................................................:.....................................................................................................................................:.........................................................................................................................................;
Apartments
south of
Costco 30 54 42 30 0
(upper
level)
............................................................................................................................................................................:................................................................:.....................................................................:.....................................................................:..................................................................:
Table 7-Sound inside the residences 10:00 p.m. — 7:00 a.m., windows open and closed
Michael R. Yantis, P.E., Hon AIA 0 206-919-9045 0 1700 Westlake Ave N., Ste 200, Seattle, WA 98109
Costco Meridian August 31, 2022
Loading Dock Sound Measurements Page 19
COMPARISON OF MEASURED SOUND LEVELS TO THE CRITERIA
Although sound associated with Costco's loading dock will be easily audible at adjacent
residences, the 24-hour Day-Night Equivalent Sound Level of 58 dBA at the residential property
to the West and 56 dBA at the apartment property to the south are substantially less than the
maximum "Acceptable" HUD level for residential property. If construction sound was not
present in the south boundary measurement, the Ldn would have been less than 55 dBA.
Early morning sound from loading dock activities could cause sleep interference if the future
residences or apartments have their windows open for ventilation. However, both properties
have air conditioning, and with their windows closed, the expected interior sound levels are
less than the 45 dBA World Health Organization criteria for maximum sound levels.
CONCLUSIONS
Based on the sound measurements at the existing loading dock and of delivery truck activities,
extending the receiving hours will not create significant impacts. Site operations will remain
compliant with the city's noise ordinance. With bedroom windows closed at nearby residences,
maximum sound levels will comply with the World Health Organizations sound level
recommendations for residential uses. No mitigation measures are needed.
Michael R. Yantis, P.E., Hon AIA • 206-919-9045 • 1700 Westlake Ave N., Ste 200, Seattle,WA 98109