2-Final Wake Stone Triangle Quarry Expansion Acoustical Study

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"
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Wake Stone Triangle Quarry Expansion Acoustical Study
Prepared For:
Wake Stone Corporation
222 Star Lane
Cary, NC 27513
Prepared By:
WSP USA, Inc.
100 Summer Street
Boston, MA 02111
Revision Date:
12 March 2021
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Table of Contents
Executive Summary...............................................................................................................Page 3
ProjectDescription................................................................................................................Page
4
Acoustical Terminology.........................................................................................................Page
6
RegulatorySetting.................................................................................................................Page
8
Existing Noise Measurements.............................................................................................Page
10
Noise Prediction Model........................................................................................................Page
17
NoiseModel Results.............................................................................................................Page
20
BlastingNoise.......................................................................................................................Page
22
BackupAlarms.....................................................................................................................Page
24
Sound Isopleth Contours.....................................................................................................Page
24
Conclusions..........................................................................................................................Page
25
Professional Qualifications..................................................................................................Page
25
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Executive Summary
A comprehensive environmental acoustical study was performed to evaluate noise
potentially generated by the expansion of the Wake Stone Triangle Quarry located at 222
Star Lane in Cary, North Carolina. The quarry has been in operation since 1982. With
approaching depletion of reserves in their existing pit (Pit 1), Wake Stone plans to expand to
the adjacent RDUAA Odd Fellows Tract for opening of a second pit (Pit 2). Concern has been
expressed for the possible noise consequences associated with the new pit expansion with
respect to noise levels propagating through the adjacent William B. Umstead State Park
(Umstead State Park).
In order to receive an expansion permit from the North Carolina Department of
Environmental Quality (NCDEQ) Division of Energy Mineral and Land Resources (DEMLR),
Wake Stone must demonstrate that noise from their new operations will not have a
"significantly adverse effect on the purposes of a publicly owned park, forest or recreation
area
To that end, this acoustical study was performed, taking into account the noise mitigation
measures that Wake Stone has already publicly committed to install. The study was
performed in accordance with the agreed and accepted methods described in Wake Stone
Noise Study Protocol dated 9/2/20. Ambient and existing operational noise levels were
measured throughout Umstead State Park, existing and future operational noise levels were
modeled to compute the changes in noise level expected in the park, and the results were
evaluated against commonly accepted definitions of significant noise impact, i.e. future noise
levels should not increase by more than 5 to 10 decibels above existing noise levels.
The results of the acoustical study found that, under worst -case noise producing conditions,
noise levels throughout Umstead State Park are expected to remain well below the 5 to 10-
decibel relative increase limit definition. Thus, Wake Stone's expansion and operation of Pit
2 are not expected to cause a significantly adverse noise impact in the park. Some particular
activities conducted in the new pit will be audible in portions of the park, just as they are
today. However, future noise levels are expected to only increase by 0 to 3 decibels
throughout the vast majority of the park.
The following report details the methodology, assumptions, noise measurement and
modeling results, relevant criteria, findings and conclusions of the acoustical study.
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Project Description
Wake Stone Triangle Quarry is located at 222 Star Lane in Cary, North Carolina. The quarry
has been in operation since 1982. With the approaching depletion of reserves in their
existing pit (Pit 1), Wake Stone plans to develop a second pit (Pit 2) on the adjoining RDUAA
Odd Fellows Tract, as shown in Figure 1. Concern has been expressed for the possible noise
consequences associated with expansion of the new pit with respect to noise levels
propagating through the adjacent Umstead State Park.
Once Pit 2 is approved for operation, the plan would include winding down and ceasing
extraction operations in Pit 1 but to still make use of the surface equipment in its current
location to process aggregate reserves excavated from Pit 2. Aggregate reserves in Pit 2 will
be loosened using controlled blasting and then loaded in trucks for transport to the existing
primary and secondary production plants. Thus in total, the only thing that's changing from
a noise perspective is where the mobile noise sources will be located.
Typical heavy earth moving equipment currently used in Pit 1 and the existing plant and
stockpile yard areas include bulldozers, backhoes, excavators, front end loaders, rock drills,
rock crushers, feeders, vibrating screens, conveyors, haul trucks, graders, water trucks,
pumps and man -lifts. Similar equipment will be used in Pit 2 also, with the exception of
stationary equipment. Blasting is anticipated to be performed a couple times a week to
loosen new material for excavation. Work hours are generally from 7 AM to 5 PM.
Figure 1. Wake Stone Triangle Quarry
Existing and Proposed Excavation Pits
Conceptual Mine Plan for Triangle Quarry Expansion
RDU MounWe
Bike Ce Mer
160 Anew.!•
U—t—d
3W. Pork
�1.
Pit 2
� 'w
4
ti
I rl
\
S
•\�.`
b�
l.V
is 'uc�r
4/29

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The Umstead State Park is a forest recreational area located immediately adjacent to the
north and east of the Wake Stone Triangle Quarry. The area is a mature forest with
approximately an even split between deciduous and conifer trees. Visitors have used the
park since 1937 for hiking, bicycling, picnicking and seasonal camping. Various trails run
through the park, with the majority of fixed sites (picnicking and camping) located relatively
close to Wake Stone's existing facilities and operations in Pit 1. To that end, moving
extraction operations to Pit 2 should be a noise benefit (i.e. reduction) for these picnic and
camping sites. There is also one residence located along Old Reedy Creek Road immediately
to the west of the new Pit 2 site at which noise levels would likely increase due to Pit 2 being
located closer to the residence than exists today for Pit 1.
Highway I-40 runs along the southern boundary of the quarry and the park causing traffic
noise to be audible in both properties. Lastly, it should be noted that the park is bordered
on the northwest by Raleigh Durham International Airport. Use of Runway 32-14 routes
aircraft directly over Umstead State Park.
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Acoustical Terminology
As with any field of science, it is critical to understand and make proper use of technical terms
and definitions that are used in the acoustical industry. Noise can be quantified in many different
manners depending on its temporal/time, tonal/frequency, or magnitude/loudness properties.
Noise magnitude is expressed in units of decibels (dB) which is a logarithmic quantity comparing
fluctuating air pressure to that of a standardized reference static air pressure of 20 micro -pascals
(i.e. dB re: 20 µPa). For this reason the noise levels that humans hear are called sound pressure
levels. Noise is expressed as a logarithmic quantity because humans are sensitive to relative
changes in noise levels. To illustrate, humans can barely perceive a change in noise level of +/-
1 decibel, can likely perceive a change of +/- 3 decibels, can easily perceive a change of +/- 5
decibels, and will generally describe a change of +/- 10 decibels as a doubling or halving in level.
With respect to tonal qualities (frequency), a frequency weighting adjustment has been
standardized to account for the human auditory response over the audible frequency range of
approximately 20 Hz to 20,000 Hz. Humans are less capable of hearing low frequency sounds,
exhibit a maximum sensitivity to tones in mid -frequency ranges, and are slightly less sensitive
to high frequency sound as well. This frequency weighted adjustment is referred to as "A -
weighting", with results expressed as A -weighted decibels, or dBA. Examples of A -weighted
decibel levels for common outdoor and indoor noise sources are provided in Figure 2.
Another common practice is to separate a sample of noise into its spectral components by using
frequency filters of known shape and bandwidth. This approach provides insights into the
source and transmission characteristics of the noise and allows for identification of frequency
ranges that contain the most acoustical energy. Octave band and third -octave band filters are
typically used for this purpose because their bandwidths are a constant percentage of their
center frequencies, and are better for mimicking how humans perceive discrete frequencies by
providing finer resolution at lower frequencies.
Numerous metrics and indices have been developed to quantify the temporal characteristics
(changes over time) of community noise that include the following:
The Equivalent Sound Level, or Leq, is the energy -averaged single noise level that represents
the same acoustic energy that was contained in the fluctuating noise level over a defined period
of time. The Leq is useful for describing the "average" sound level over a defined period of time,
and is expressed in dBA.
The Maximum and Minimum Sound Levels, or Lmax and Lmin, are the loudest and quietest
instant sound levels occurring during a period of time. The Lmax is particularly useful for
evaluating loud, impulsive noise events. Lmax and Lmin levels are expressed in dBA, however
the root -mean -square (RMS) time constant of the sound level meter's detector has a significant
effect on the measured levels. By International agreement, a sound level meter with an RMS
response set to 'slow' (Lmaxs) has a rise time constant of 1 second, where a setting of 'fast'
(Lmaxf) is about 8x faster with a rise time constant of only 0.125 seconds.
The Day Night Sound Level, or Ldn, is a 24-hour community noise metric in which a 10 decibel
adjustment has been added to the measured hourly Leq levels from 10 PM to 7 AM to account
for people's greater sensitivity to noise intrusion at night. The Ldn metric is used in many federal
noise guidelines to assess the long-term effects of transportation sources.
The Sound Percentile Level, or Ln, expressed in dBA is a statistical representation of changing
noise levels indicating that the fluctuating noise level was equal to, or greater than, the stated
level for "n" percent of the time. For example, the L1, L10, L50, and L90 represent the noise
6/29

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levels exceeded 1%, 10%, 50%, and 90% of the time. The L10 is often used to identify impacts
of transportation or construction noise sources, while the L90 is considered to represent steady
background noise.
Figure 2. Common A -Weighted Decibel (dBA) Sound Levels
Noise Scale: Common Sound Levels
Common Outdoor Noise Level Common Indoor
Sound Levels dB (A) Sound Levels
110
100
B-747-2007akeoff at 2 mks
Gas lawn Mower at 3 feet
Diesel TPA
90
att2ofcet
0C430TakwfF
at 2 mies
�
Maim Metropolis Daytkne
13-7577akeoff at2 miles
HghwayTrafkatsofeet
70
ZommerdaI
f+rea
60
Suburban4aytime
QuieludsanDaytime
So
Rural Daytime
Quiet Urban
Nighttime
40
Quiet Suburban
Nighttime
aD
Quiet Rural Nighttime
20
10
C
110 Rack Hand
Inside Subway 13
1D0 Trees
(New Yank}
Foodulender
90 at3feet NO
Laud Voice
so Garbage Disposal
at 3 feet
70 Vacuum Cleaner at10feet
Normal Speech
W
Large Business Office
50 Dishwasher Next Room
Refrigerator
SmallThater
4D largeConferenceRoom
(rd)
library
30 BedtmmatNight
Concert Hall
(Badcgroursdl
2D
Broadcast& Recording Studio
1D
D Threshohdof
Hearing —
The Sound Power Level (PWL) of a noise source is the strength or intensity of noise that the
source produces/emits regardless of the environment in which it is placed. Sound power is a
property of the source, and therefore is independent of distance. The radiating sound power
then produces a Sound Pressure Level (SPL) at any given point of interest which human beings
perceive as audible sound. The sound pressure level is dependent on its environment
(absorption, reflections, etc.) and its distance from the noise source. And even though both
sound power and sound pressure are expressed in decibels (dB), they are not the same thing and
should not be confused. Decibel levels of sound power are referenced to a power level of 1 pW,
while decibel levels of sound pressure have a pressure reference level of 20 µPa.
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Regulatory Setting
According to the North Carolina Mining Act of 1971 administered by the North Carolina
Department of Environmental Quality (NCDEQ) Division of Energy Mineral and Land
Resources (DEMLR), Wake Stone must obtain a modification of their current Mining Permit
in order to expand their operations. Wake Stone must demonstrate that noise from their
new operations in Pit 2 will not have a "significantly adverse effect on the purposes of a
publicly owned park, forest or recreation area".
However, the Mining Act does not quantitatively define what is meant by "significantly
adverse effect". Thus, a task in this study involves research into the noise guidelines
promulgated by other federal and state agencies with respect to noise impact for an outdoor
park land -use. Table 1 summarizes some of these other noise guidelines.
The natural soundscape is comprised of physical and biological sounds. Physical sound is
created by wind, rivers, rock falls, etc., whereas biological sound is created by animals, birds
and insects. Different habitats have specific soundscape characteristics depending on the
climate, landscape and animal population. Evaluation of the level of impact on natural
soundscape generated by human activity is dependent on the specific habitat in question.
The State of North Carolina does not regulate noise, so the responsibility is on the local
governments. Noise ordinances of the counties where Wake Stone operations occur do not
specifically mention noise criteria for parklands. In order to determine the noise criteria
applicable for parklands, guidance documents published by various agencies were reviewed
and the quantitative recommendations are summarized below.
Table 1. Various Noise Criteria for Parklands and Wilderness Areas
Guidance Source
Recommended Noise Criteria
US National Parks Services (NPS)
45 dBA L10 and 38 dBA L50
US Federal Highway Administration (FHWA)
57 to 67 dBA Leq(1hr)
US Federal Railroad/Transit Administrations (FRA/FTA)
+5 to +10 dBA Leq(h) above Ambient
US Federal Aviation Administration (FAA)
70 to 75 dBA Ldn
US Environmental Protection Agency (EPA)
70 dBA Leq(24hr) or 55 dBA Ldn
Federal Energy Regulatory Commission (FERC)
55 dBA Ldn and 49 dBA Leq
Federal Interagency Committee on Noise (FICON)
+5 dBA if Ambient is <60 dBA, +3 dBA if 60-65dBA, +2 dBA if Ambient is >65 dBA
World Health Organization (WHO)
50 to 55 dBA Leq
North Carolina Department of Transportation (NCDOT)
67 dBA Leq(h) or an increase of +10 dBA
Massachusetts Environmental Protection (MassDEP)
Increase of +10 dBA above L90 Ambient
Washington State
55 dBA 07:OOAM to 10:OOPM
45 dBA 10:OOPM to 07:OOAM
Minnesota State
65 dBA L10, 60 dBA L50, 07:OOAM to 10:OOPM
55 dBA L10, 50 dBA L50, 10:OOPM to 07:OOAM
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The US National Parks Service (NPS) recommended noise criteria is mostly intended for non -
metropolitan area national and state parks. Umstead State Park is located within an
expanding metropolitan area. As such, stringent NPS recommended criteria of 45 dBA L10
and 38 dBA L50 is too conservative. The Federal Energy Regulatory Commission (FERC)
guidance document "Guidance Manual for Environmental Report Preparation, February2017'
is intended for natural gas projects and pipelines. Section 4.9.2 of the FERC guidance
document recommends a continuous noise level of 49 dBA Leq as criteria for Noise Sensitive
Areas (NSA) which include parklands, campgrounds, and wilderness areas. This criteria can
be adopted for quarry operations in proximity to parklands, however absolute noise level
limits do not apply well in this situation given the fact that the Wake Stone Triangle Quarry
has been in operation since 1982, and the location is in a metropolitan area surrounded by
busy state and interstate highways. The focus should be placed on how much more noise
might Wake Stone be producing in the future when Pit 2 is opened for operation.
As shown in the previous section, humans can barely perceive a change in noise level of +/-
1 decibel, can likely perceive a change of +/- 3 decibels, can typically perceive a change of +/-
5 decibels, and will generally describe a change of +/- 10 decibels as a doubling or halving in
level. From this commonly accepted subjective response description, acousticians and
regulatory agencies have generally agreed that a 5-decibel increase would represent the
onset threshold of audible changes, and a 10-decibel increase would be a significant noise
impact.
Moreover, the State of North Carolina Department of Transportation (NCDOT) has defined
the term substantial noise increase in their Traffic Noise Policy dated 10/6/16. In it, a
receptor is considered impacted by noise if the predicted future hourly Leq equivalent noise
level exceeds the existing ambient Leq noise level by 10 decibels or more.
Consequently, where a 5-decibel increase might be perceptible, it requires a greater increase
in noise level to constitute a significant increase. Thus, this acoustical study has defined a
"significantly adverse effect" as meaning a 10 decibel or more increase in future noise
levels when compared to existing noise levels.
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Existing Noise Measurements
Existing ambient noise measurements were performed in and around Umstead State Park
from 11/16/20 to 11/23/20 and again from 12/7/20 to 12/14/20. Long-term noise
measurements lasting a week were performed at the six monitoring locations (LT-#) shown
in Figure 3. The purpose of the long-term noise measurements were two fold, (1) to
document actual existing noise conditions at selected locations throughout the park, and (2)
to serve as a measured noise level against which modeled existing noise levels could be
compared to ensure the model was performing as expected.
Larson Davis Model 720 (LD-720) environmental noise monitors were used to measure the
long-term noise data. The monitors were checked for proper calibration before and after
use using a Bruel & Kjaer Model 4231 acoustical calibrator. As such, the noise monitoring
system met or exceeded the accuracy requirements found in ANSI Standard S1.4 for Type 2
quality. The monitors were deployed in trees at the respective sites and the microphones
were covered with windscreens. Noise data was digitally stored in hourly intervals with
noise metrics including Leq, Lmax, Lmin, L1, L10, LSO and L90 sound levels. All sound levels
were expressed in A -weighted decibels (dBA) using an RMS `slow' response.
Figure 3. Long -Term Ambient Noise Monitoring Sites
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The averaged results of the long-term noise monitoring data are summarized in Table 2 for
the hours of 7:00 AM to 5:00 PM during which time Wake Stone is typically operating. Three
scenarios are provided, (1) time periods when the quarry was in full production mode, (2)
periods when the quarry was on a reduced work schedule performing mostly maintenance
activities, and (3) Sunday periods when no work was being performed.
The results in the table indicate that noise produced by existing operations in Pit 1 may be
audible throughout the park but only to a minor degree when compared to the relatively low
noise produced during maintenance periods. Interpreting results relative to no work periods
is difficult because all transportation and community noise sources are less noisy on
Sundays.
Table 2. Measured Leq Noise Levels During Work Hours
Site
No.
Location in
Umstead State Park
Measured Leq (7AM - 5PM) dBA
Difference vs.
Production dB
Production
Main-
tenance
Sunday
No Work
Main-
tenance
Sunday
No Work
LT-1
Picnic Grounds
53
51
48
-2
-5
LT-2
Company Mill Trail
50
49
46
-1
-5
LT-3
Residence Property Line
55
57
53
1
-3
LT-4
Mid Gate
52
48
45
-3
-6
LT-5
Trenton Road Gate
51
49
46
-2
-5
LT-6
Sendero Gate
47
43
43
-4
-4
Note: Sound levels rounded to the nearest full decibel.
The results of the six long-term noise monitors are shown in Figures 4 thru 9. The data
collected over the week was reduced by averaging the results of each corresponding hour
during the week. Thus the results yield typical hourly noise levels that can be expected at
each monitoring location. The blue dot is the computed Ldn level and the average Lmax, Leq,
and L10 and L90 percentile levels are shown for each hour. The Lmax level could have been
caused by any loud event such as a nearby bird chirp, crow call, aircraft, or noise produced
by Wake Stone's operations. The Leq, L10 and L90 results are more indicative of constant
noise levels throughout the park. The effects of morning and evening commuter traffic (i.e.
rush hour) is evident centered around 7:00 AM and 5:00 PM, respectively. More notably, the
L10 levels at all sites are already well above the National Park Service's recommended noise
guideline of 45 dBA L10 at all times of day and night regardless of Wake Stone's operations.
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Figure 4. Long -Term Ambient Noise Levels for Site LT-1
Typical 24-hour Ambient Noise Levels
Umstead Park, Site 1
11/16/20 - 11/23/20
90
85 -
80
a 75 -
0
N 70 _ _ -
41
a
"m0 65 -
v
J 60 - 55
- - _
N
Z
W - T T
90
45 �7
40 - --
35 - ---
30 JE
v 8 8 8$ 8
o .y ry m a �n e n m c, a
Time of Day (Start of Hour) . ~ . . ~ . ry ry ry ry
-Lmax -Leci -L70 -L.
Figure S. Long -Term Ambient Noise Levels for Site LT-2
Typical 24-hour Ambient Noise Levels
Umstead Park, Site 2
11/16/20 - 11/23/20
90
85 MH
80
a 75
3
N
�. 70
Q
'm0 65 -
W
y 60 -
J
W
a 55 AV
Z
'D
50 -
m
45
40 - -- --- - --- -- -
35
30
i 8 8 8 8 8 8 8 8 8 8 0 0 0 0 0 0 0
a
Time of Day (Start of Hour) . . . . . . ry ry ry ry
-Lmax -Leq -L10 -L90
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Figure 6. Long -Term Ambient Noise Levels for Site LT-3
Typical 24-hour Ambient Noise Levels
Umstead Park, Site 3
12/7/20 - 12/14/20
90
85
so
d 75 -
0
N
.. 10 -
0
a
0 65
v
'w eo
w
0 5s —
z
50
m
as
40 - - - --
35 ----.--- --- -----.--- ------ ---------
30
v 8 8 8$ 8
o .y ry m a �n e n m c, a
Time of Day (Start of Hour) . ~ . . ~ . ry ry ry ry
—Lmax —Leci —L70 —L.
Figure 7. Long -Term Ambient Noise Levels for Site LT-4
Typical 24-hour Ambient Noise Levels
Umstead Park, Site 4
12/7/20 - 12/14/20
90
85
80
a 75
3
O
N 70
Q
y 65 - -- —
W
60 _
d
0 --
z
a
50 —
m
45 — — — — — — — t
40 — — — — -- - - - �-4 —
35
30
8 8 8 8 8 8 8 8 8 8 0 0 0 0 0 0 0
o .. ry rci a m n m m a
Time of Day (Start of Hour) ry ry ry ry
�Lmax —Leq —L10 —L90
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Figure 8. Long -Term Ambient Noise Levels for Site LT-5
Typical 24-hour Ambient Noise Levels
Umstead Park, Site 5
11/16/20 - 11/23/20
90
85
80
a 7570
--dt 1— — — — — — — —
—
N
Q
M 65 -
N
v 60 —.00
a 55 — —
ZIs
Ooo
m
45
-o" 7T
40 -
35 — ---
30
J g g g 8 8 g S g 8 8 e
o e vi �e co v
Time of Day (Start of Hour)
—Lmax —Leq — L30 —L90
Figure 9. Long -Term Ambient Noise Levels for Site LT-6
Typical 24-hour Ambient Noise Levels
Umstead Park, Site 6
11/16/20 - 11/23/20
90
85
80 —
a 75
7
N
.�. 70
Q
� 65 — —
y60
J
W
0 55 - —'
\ [12
50
m
45
40 --- — —
35 --- —
30
i 8 8 8 8 8 8 8 8 8 8 0 0 0 0 0 0
if
Time of Day (Start of Hour)
—Lmax —Leq —L10 �L90
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In addition to long-term monitoring, short-term noise measurements, lasting 15 minutes,
were also manually performed at four selected sites in Umstead State Park during the weeks
of 11/16/20 to 11/23/20 and 12/7/20 to 12/14/20. A Svantek Model 971 (SV-971) sound
level meter was used for these measurements, which meets the requirements for ANSI
Standard S1.4 for Type 1 accuracy. The purpose of the short-term noise measurements was
to positively identify and correlate audible noise sources with the sound levels being
measured. This was particularly important to perform during the production blasts
occurring during the monitoring periods.
Short-term noise data was collected during full quarry operation with blasting in the
morning and the afternoon, full quarry operation with no blasting in the morning, reduced
quarry operation maintenance day in the afternoon, and in the morning with the plant
closed. A summary of the short-term noise data results are shown in Table 3.
While in Umstead State Park, noticeable noise sources included traffic noise from local roads,
overhead aircraft and helicopter noise from RDU airport, and typical nature noise, such as
running water, rustling leaves, birds, and insects. At monitoring locations closest to the
quarry, noise levels between the quarry and I-40 were nearly indistinguishable, except for
the backup alarms from equipment operating in the quarry. During blasting, warning sirens
employed prior to the blast could be heard from inside Umstead State Park. The blast, which
only occurs for a fraction of a second, was noticeable by ear and could be felt as well as being
heard. A final siren followed the blast for about one minute.
Table 3. Short -Term Noise Measurements Results
Site No.
Site Location
Measured Short -Term Noise Level
L10 dBA
Leq dBA
L90 dBA
ST-7
Foxcraft Lake
47
45
42
ST-8
Entrance Gate Trail
46
44
41
ST-9
I-40 & Old Reedy Creek Road
71
70
68
ST-10
Campgrounds
43
42
38
Note: Sound levels rounded to the nearest full decibel.
The measurement data was later reviewed to identify and isolate the blast event that
occurred during short-term measurements at sites ST-7 and ST-8 on 11/18/20 at 13:40. The
sound level data was stored in 1-second intervals and an audio wavefile was recorded
throughout the measurement. The recorded wavefiles were listened to while simultaneously
viewing the measured noise data in order to audibly identify the 1-second interval where the
maximum sound level from the blast occurred. The noise level during the blast was 59 dBA
at Site ST-7 and 47 dBA at Site ST-8. The measured blast sound level was later also used to
estimate the sound power emission of the blast for use in the noise model.
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Further analysis was conducted by comparing the noise produced by the blast event to that
of other common environmental sound sources of comparable loudness captured during the
15-minute short-term noise measurements. In this case, as shown in Figure 10, two aircraft
overpasses were identified as being within 5 decibels of the blast noise level. The vertical
axes of the charts are the same scale for ease in visual comparison.
Figure 10. Comparison of Blast Noise Level to Other Noise Sources
Blast Event: 59 dBA Leq(1s) at Site M-7 on 11/18/20
dB dB
60
60
55
55
°u
u
40
____. ____ _ ____ __. __ ...
40
01:38:30 PM 01:38:45 PM 01:39:00 PM 01:39:15 PM 01:39:30 PM 01:39:45 PM 01:40:00 PM 01:40:15 PM 01:40:30 PM 01:40:45 PM 01:41:00 PM Time
Aircraft Overpass: 54 dBA Leq(1s) at Site M-7 on 11/23/20
dB 113
60
60
55
____ ....
55
N S0
50 w
m
o
45
�
45
40
_.
40
09:01:15 AM 09:01:30 AM 09:01:45 AM 09:02:00 AM 09:02:15 AM 09:02:30 AM 09:02:45 AM 09:03:00 AM 09:03:15 AM 09:03:30 AM 09:03:45 AM Time
Aircraft Overpass: 55 dBA Leq(1s) at Site M8 on 11/23/20
dB dB
60
60
55
5S
50
____
50
N
m
40
__ ____. ____. ____. ____. ___.
40
09:28:30 AM 09:28.45 AM 09:29:00 AM 09:29:15 AM 09:29:30 AM 09:29:45 AM 09:30:00 AM 09:30:15 AM 09:30:30 AM 09:30:45 AM 09:31:00 AM Time
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Noise Prediction Model
Noise levels associated with operation of the existing quarry (Pit 1) and future quarry (Pit 2)
were predicted using the Cadna-A® noise model, developed by DataKustik, GmbH. The
Cadna-A model implements ISO Standard 9613 for environmental noise sources and outdoor
sound propagation. It is a comprehensive, three-dimensional, ray -tracing model in which
noise sources are assembled from point, line and/or area components each emitting sound
power levels (PWL) in octave bands or broadband A -weighted format. Distance losses,
elevation differences, ground attenuation, wind effects, building shielding, attenuation
through walls, and barrier/berm effects are computed in the Cadna-A model, and the
resulting sound pressure levels (SPL) are predicted at any number of receptors of interest.
As is standard practice, all receptors were modeled at a height of 5 feet above the ground.
As shown in Figure 11, the Cadna-A base model for the project was developed by importing
geo-referenced aerial imagery along with topographic contour data in 2-foot intervals. The
topographic contour data was provided by Wake Stone for the quarry areas and current
North Carolina One -Map Lidar data was used for the surrounding regions of the study area.
Conservative worst -case noise assumptions were used in populating the model. For example,
all noise -producing equipment was assumed to be operating simultaneously. A ground
factor of G=1.0 for soft ground was set as the default for the model. Specific areas with
different ground types were then defined, including the quarry site with G=0.5 for mixed
hard and soft ground, and water and paved areas with G=0.0 for hard ground. To represent
worst -case noise conditions during winter when leaves would be off trees, areas with foliage
were not included in the Cadna-A model. And it should be noted that per ISO 9613, a
"favorable wind condition" was assumed in the model in which a mild wind blows towards
each receptor regardless of where the noise sources are located. A brief summary of the
conservative assumptions incorporated into the noise model include:
• All equipment on site, including mobile and
stationary equipment, were assumed to be
operating simultaneously based on their
usage factors averaged over a full week.
• Less -absorptive ground factors were
assumed for areas not covered with foliage
such as for the quarry site with loose dirt
piles and water surfaces, as shown in the
picture to right.
• Blasting, which will only occur a couple
times a week, was assumed to be occurring
during the typical hour (i.e. worst -case)
averages reported herein.
• No attenuation was assumed for foliage.
• Favorable wind conditions blowing from the
noise source towards each receptor was
assumed.
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Figure 11. Perspective View of Cadna-A Noise Model (Looking Northeast)
The Cadna-A base model was then configured to estimate noise levels generated by the
quarry operations for the following conditions:
• Existing Production - includes the current production activities in Pit 1, hauling of rock
to the primary crusher, and typical crushing, plant and yard operations.
• Future Overburden Clearing - includes clearing of overburden at the expansion Pit 2
and hauling of overburden across the proposed Crabtree Creek Bridge to the overburden
storage area on the west side of Pit 1. This condition also includes the same typical
crushing, plant and yard operations as the Existing Production condition.
• Future Production - includes production at the expansion Pit 2 and hauling of rock
across the proposed Crabtree Creek Bridge around the north side of the existing Pit 1 to
the primary crusher. This condition also includes the same typical crushing, plant and
yard operations as the Existing Production condition. The Future Production condition
was further divided into four scenarios (280-foot, 266-foot, 210-foot and 160-foot) based
on the elevation of projected working benches in the expansion Pit 2. These scenarios
were modeled individually to represent how the production work will decrease in
elevation over time as the new pit is excavated. It should be noted that worst -case noise
producing condition occurs when equipment is operating at grade, i.e. Future Production
at 280 feet.
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For each of these conditions, noise levels generated by the quarry were estimated for a
typical hour of operations with all equipment operating. Noise model inputs included:
• The locations of existing and future production areas where mobile equipment would be
operating, haul truck routes, customer truck routes, and locations of all crushers,
conveyors, plant and yard equipment.
• Sound power levels of mobile equipment were primarily derived from noise emission
measurements taken during Wake Stone quarry operations. For stationary processing
plant equipment (crushers, screens, and conveyors), sound power levels were estimated
based on a review of technical literature for similar equipment. For mobile heavy
equipment sound power emission levels were taken from the FHWA's Roadway
Construction Noise Model (RCNM).
• The estimated number of hours per week, obtained from Wake Stone, that each piece of
mobile and stationary equipment is used during a typical 50-hour work week was used
to calculate a usage factorM representing the percentage of time each piece of equipment
is operating during a typical hour of production. The equipment -specific usage factors
were then applied as an adjustment to the equipment sound power levels within the
Cadna-A model.
• For the future overburden clearing and production scenarios, proposed terrain contour
lines in 2-foot intervals for the expansion Pit 2, widening of haul roads, and the new
bridge over Crabtree Creek were also included.
• For the future overburden clearing and production scenarios, two noise mitigation
measures that Wake Stone has already committed to were included in the noise model:
1. An approximately 15-foot tall earthen berm on the north and west sides of the
expansion Pit 2.
2. An approximately 14-foot tall noise wall to the north of the haul road along the north
side of the existing Pit 1.
As is standard practice, noise emitted by backup alarms was not included in the noise model.
This is due to several reasons, (1) it can be difficult to anticipate where and when a vehicle
will need to backup, (2) the alarms are a required safety device, and (3) the alarms are not
that loud with respect to receptors located more than a few hundred feet away. For example,
a typical loud pure -tone backup alarm might emit a sound level of 105 dBA Lmax at 4 feet
behind the vehicle. This would reduce to only 77 dBA Lmax at 100 feet, and would be down
to 63 dBA Lmax at 500 feet. When averaged over an hour, the results would be negligible.
Note (*) - The acoustical usage factor is the standard way that construction equipment noise
is computed when averaging it over some time period. It takes into account the fraction of
time the equipment is operating at full power (i.e. loudest) during a typical work shift, in this
case averaged over a 50 hour work week. The acoustical usage factor affects the resulting
Leq sound levels, but the generated Lmax sound levels remain unchanged.
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Noise Model Results
Once the Cadna-A model was fully populated, it was allowed to run to compute resulting
sound levels for the various quarry operating conditions at eight discrete receptor locations
(R-#) in Umstead State Park as shown in Figure 3. Six of the receptors were selected to
correspond with the long-term noise monitoring sites, and another two receptors were
added in response to requests from DEMLR. The results are summarized in Table 4 and are
expressed as typical hourly equivalent sound levels (Leq(1hr)) in A -weighted decibels (dBA).
Again, the results shown in the table represent realistic worst -case conditions that assume
all quarry equipment is running simultaneously.
As can be seen in Table 4, sound levels from future Pit 2 operations are expected to range
from 31 to 55 dBA Leq(1hr) across all eight discrete receptor locations in Umstead State
Park. Naturally, the louder sound levels will occur closer to the quarry work, and the quieter
sound levels will occur farther away. This range of anticipated sound levels compares very
closely with the sound levels produced by existing quarry operations in Pit 1 which range
from 31 to 52 dBA Leq(1hr).
The results in Table 4 for receptors R-2 and R-3 are of particular significance from the point
of view of ensuring that the Cadna-A noise model is calculating correct noise levels.
Receptors R-2 and R-3 are the closest to Wake Stone's existing work in Pit 1. As such, it
would be reasonable to expect that the measured and modeled noise levels at these two
receptors should match relatively closely. As can be seen, the model is nearly perfectly
calibrated with the measured noise results for existing noise during production hours. Thus,
the model can be relied upon to predict accurate future noise levels as well.
Table 4. Predicted Existing and Future Sound Levels for Quarry Operations
Receptor
Measured
Predicted Average Hourly Noise Level, dBA Leq(1hr)
Existing
Production
dBA Leq
Existing
Quarry
Overburden
Stripping
Production
280 ft
Production
266 ft
Production
210 ft
Production
160 ft
Existing I-40
Traffic
R-1: Residence Property Line
LT-3: 55
46
49
49
48
47
46
58
R-2: Company Mill Trail
LT-2: 50
50
51
52
52
52
52
38
R-3: Picnic Area
LT-1: 53
52
52
52
52
52
52
50
R-4: Residences
LT-5: 51
35
35
35
35
35
35
47
R-S: Reedy Creek Park Trail
LT-4: 52
37
38
39
39
38
38
39
R-6: North Turkey Creek Trail
LT-6: 47
31
31
31
31
31
31
29
R-7: Foxcroft Lake
N/A
50
55
53
53
52
52
45
R-8: Crabtree Creek
N/A
48
49
50
50
50
50
38
Note: Sound levels rounded to the nearest full decibel.
Table 4 also shows the predicted sound level attributable solely to traffic on I-40. These
results are shown only for comparative purposes and have no bearing on the current noise
analysis. The traffic noise levels were not measured; they were computed using the Cadna-
A model by imputing traffic volumes, fleet mixes (i.e. trucks and cars) and speeds counted
during the 15-minute short-term noise field measurements (expanded to a full hour). The
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model can then compute just traffic noise (no other sources) in the surrounding vicinity in
accordance with FHWA/NCDOT guidelines. It should be noted that the results shown herein
are based on just one traffic count observance during a time frame when traffic volumes still
might be lower than is typically the case due to COVID restrictions.
Of more importance for the intent and goal of this study, the results in Table 5 show the
noise delta increase (+) or decrease (-) for future Pit 2 operations relative to existing sound
levels produced by Pit 1 operations. As can be seen, once the overburden has been cleared,
none of the receptors are expected to be exposed to a noise increase greater than 3 decibels
during all phases of production for Pit 2. In fact, the majority of receptors will not experience
an increase of more than 1 decibel. For perspective, such minor noise level increases are
typically considered to be trivial and insignificant from an acoustical engineering
perspective.
During the overburden stripping phase, future sound levels will be no louder than what is
expected during the various production phases except at receptor R-7 Foxcraft Lake which
might experience a temporary 4 decibel increase.
Consequently, it can be concluded that noise levels associated with Wake Stone's future
operations involving Pit 2 are expected to remain well below the selected 10-decibel
increase criterion, and thus will not pose a "significantly adverse [noise] effect on the
purposes of a publicly owned park, forest or recreation area [in Umstead State Park]".
Table 5. Expected Differences in Sound Levels for Quarry Operations
Receptor
Predicted Future re: Existing Noise Level Delta, dB
Overburden
Stripping
Production
280 ft
Production
266 ft
Production
210 ft
Production
160 ft
Production
280 ft vs 1-40
Traffic
R-1: Residence Property Line
3
3
2
1
1
-10
R-2: Company Mill Trail
0
2
2
2
2
14
R-3: Picnic Area
0
0
0
0
0
2
R-4: Residences
0
1
1
0
0
-12
R-5: Reedy Creek Park Trail
1
1
1
1
1
-1
R-6: North Turkey Creek Trail
0
1
1
1
1
2
R-7: Foxcroft Lake
4
3
3
2
2
8
R-8: Crabtree Creek
1
2
2
2
2
1 12
Note: Sound levels rounded to the nearest full decibel.
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Blasting Noise
Concern over blasting noise affecting Umstead State Park has garnered significant attention
during this process. To be clear, controlled blasting occurs now in existing Pit 1. Future
blasting in expansion Pit 2 would be very similar in terms of noise event magnitude (i.e.
similar charge weights) and occurrence (i.e. only a couple times per week). Warning sirens
will continue to be used as they are today.
To evaluate the significance of blasting noise, the same Cadna-A model was used to predict
sound levels in Umstead State Park attributable solely to a typical blast event. Sound power
data to model the blast was back -calculated from the short-term noise measurements
performed in the park during monitoring period blasts, as shown in Figure 10. The results,
as summarized in Table 6, were then computed for the maximum sound level (Lmax)
expected during a blast event expressed in A -weighted decibels (dBA) using an RMS `slow'
time response. The'slow' time response was selected to be consistent and allow comparison
with many of the other park noise criteria presented in Table 1.
As can be seen in Table 6, sound levels from blasting in future Pit 2 are expected to range
from 44 to 73 dBA Lmax across all eight discrete receptor locations in Umstead State Park.
Naturally, the louder sound levels will occur closer to the quarry work, and the quieter sound
levels will occur farther away. For comparison, this range of anticipated sound levels
produced by existing blasting operations in Pit 1 range from 38 to 57 dBA Lmax. It is
important to note that sound levels on these orders of magnitude do not represent a concern
for inducing hearing damage for anyone exposed to them.
Table 6. Predicted Existing and Future Sound Levels from Blasting
Receptor
Predicted Blasting Noise Level, dBA Lmax slow
Existing
Quarry
Overburden
Stripping
Production
280 ft
Production
266 ft
Production
210 ft
Production
160 ft
Existing 1-40
Traffic
R-1: Residence Property Line
51
N/A
73
72
69
67
58
R-2: Company Mill Trail
57
N/A
64
63
59
53
38
R-3: Picnic Area
52
N/A
60
61
60
60
50
R-4: Residences
38
N/A
47
48
47
47
47
R-5: Reedy Creek Park Trail
42
N/A
54
53
51
47
39
R-6: North Turkey Creek Trail
41
N/A
44
44
44
44
29
R-7: Foxcroft Lake
54
N/A
71
69
64
62
45
R-8: Crabtree Creek
57
N/A
64
63
59
57
38
Note: Sound levels rounded to the nearest full decibel.
Blasting is not expected to be needed during removal of overburden.
Blasting noise Lmax data shown for information only - not used for noise evaluation purposes - but is
included in the modeled typical hour Leq noise levels.
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The results in Table 7 show the noise delta increase (+) or decrease (-) for future Pit 2
blasting events relative to existing sound levels produced by Pit 1 blasting events. As can be
seen, blasting noise levels will remain readily audible throughout Umstead State Park but
will reduce somewhat as the floor elevation of Pit 2 decreases. The loudest increase in
blasting noise levels are expected near receptor R1 on the west side of the new quarry Pit 2.
This is attributable to Pit 2 being physically much closer to receptor R1 than Pit 1 is today.
There will be some noise reduction shielding provided by the 15-foot earthen berm that
Wake Stone has committed to erect along the property boundary with receptor R1.
Thus, even though future blasting noise will be louder in some locations, it should not be
used as a measure for compliance with the 10-decibel increase criterion due to how
infrequently blasting will occur, the short impulsive nature of the blasting event, and the fact
that identical blasting occurs today in the existing Pit 1.
Table 7. Expected Differences in Sound Levels for Blasting Events
Receptor
Predicted Future re: Existing Blasting Noise Level Delta, dB
Overburden
Stripping
Production
280 ft
Production
266 ft
Production
210 ft
Production
160 ft
Production
280 ft vs 1-40
Traffic
R-1: Residence Property Line
N/A
22
21
19
17
14
R-2: Company Mill Trail
N/A
6
6
2
-4
25
R-3: Picnic Area
N/A
9
9
8
8
10
R-4: Residences
N/A
9
9
9
9
0
R-5: Reedy Creek Park Trail
N/A
11
11
8
5
14
R-6: North Turkey Creek Trail
N/A
4
4
4
4
16
R-7: Foxcroft Lake
N/A
17
15
10
8
26
=R-8-.abtree Creek
N/A
7
6
2
0
25
Note: Sound levels rounded to the nearest full decibel.
Blasting is not expected to be needed during removal of overburden.
Blasting noise Lmax data shown for information only - not used for noise evaluation purposes - but is
included in the modeled typical hour Leq noise levels.
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Backup Alarms
Loud backup alarms are typically the number one source of noise complaints from the public
at any construction site due to their intentionally annoying pure -tone beepers. Their purpose
is paramount for protecting the life and safety of people working near the equipment. The
Mine Safety and Health Administration (MSHA) does not require a specific sound level for
backup alarms to emit; they simply state that the backup alarm "shall be audible above the
surrounding noise level".
To this end, Wake Stone will replace the standard backup alarms on their equipment with
either manually -adjustable or ambient -sensitive models. These quieter backup alarms
produce tone levels approximately 20 decibels quieter (i.e. about a quarter as loud)
compared to a standard backup alarm.
An even more attractive backup alarm from a community noise perspective is one such as
the BBS-TEK Series of backup alarms manufactured by Brigade Electronics https://brigade-
electronics.com/products/reversing-and-warning-alarms/ (or equivalent). These alarms
produce a much less annoying broadband "white noise" sound rather than a pure -tone.
Wake Stone will evaluate the suitability of the various quieter backup alarms based on safety,
cost and effectiveness and install them as needed.
Sound Isopleth Contours
The Cadna-A model also produces sound isopleth contour lines of equal loudness
attributable only to Wake Stone's noise production (i.e. not including any other background
noise sources). Figure 12 illustrates the sound contour lines for the existing condition, i.e.
operations occurring in Pit 1. Similarly, Figure 13 shows the sound contour lines for the
worst -case future noise condition, i.e. production occurring in Pit 2 at the surface elevation
of 280 feet. The contours are drawn in 5-decibel increments represented by the color
gradient in the legend. The purple dashed line around the outside shows the extents of
Umstead State Park and the area within which the sound contours were computed.
Careful examination of the two figures shows how noise produced by only Wake Stone's
operations emanate from the pits, interacts with the surrounding topography, and
propagates with varying efficiency in various directions. Interpolation between the contour
lines allows for the estimation of quarry -generated sound levels at any point of interest
within Umstead State Park. The sound contours do not represent total sound levels (i.e.
cumulative noise levels), nor do they necessarily represent the predominant noise at any
given location. They only represent the modeled noise contribution of quarry activities.
Lastly, Figures 14 and 15 show isopleth contour areas for the delta or difference between
the sound levels produced in the future versus existing quarry operating conditions. The
first figure shows the quarry site and immediate vicinity. The second figure shows Umstead
State park in its entirety. As can be seen in the three shades of green, the vast majority of
Umstead State Park is expected to experience a noise increase of less than 3 decibels due to
Wake Stone's operations expanding from Pit 1 to Pit 2. In fact, more than half of the park
will experience an increase of less than 1 decibel.
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Conclusions
A comprehensive acoustical study was performed for the Wake Stone Triangle Quarry to
evaluate the potential for expanded operational noise produced in the future to impact
outdoor recreation areas in the adjacent Umstead State Park. Various noise guidelines were
considered, existing noise levels were measured, and existing and future noise levels were
modeled. The results indicate that operating noise from the future Pit 2 will only increase
noise levels throughout the vast majority of Umstead State Park by less than 3 decibels; well
below the recognized definition for a substantial noise increase impact of 10 decibels. Thus,
it can be concluded that expansion of Wake Stone's operations into Pit 2 will not pose a
'significantly adverse [noise] effect on the purposes of a publicly owned park, forest or
recreation area (in Umstead State Park]".
Professional Certification
I hereby certify that this plan, specification, or report
was prepared or reviewed by me and that I am a duly
certified acoustical professional as recognized by the
Institute for Noise Control Engineering (INCE).
Erich Thalheimer
WSP USA, Inc.
Principal Noise & Vibration Engineer
INCE Board Certified No. 20104
in0E
The Institute of Noise Contml Engineering
of the United States of America, Inc.
in recognition of
professional standing and contributions
attests that
ERJCH THALHEIMEIZ
a Member of the Institute
is
Board Certified
in Noise Control Engineering
F., the 3-rd of ol—t—
1' p�
2001.7unc
20104
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Figure 12. Isopleth Sound Contours for the Existing Condition
Note: Sound isopleth contour levels attributable only to noise produced by Wake Stone's operations (i.e. does not include other
background noise sources such as traffic noise from I-40 or aircraft noise from Raleigh Durham Airport).
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Figure 13. Isopleth Sound Contours for the Future Condition
Note: Sound isopleth contour levels attributable only to noise produced by Wake Stone's operations (i.e. does not include
other background noise sources such as traffic noise from I-40 or aircraft noise from Raleigh Durham Airport).
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Figure 14. Quarry Site Isopleth Sound Difference Contours (Future - Existing)
Note: Sound isopleth contour levels attributable only to noise produced by Wake Stone's operations (i.e. does not include
other background noise sources such as traffic noise from I-40 or aircraft noise from Raleigh Durham Airport).
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Figure 1S. Park Area Isopleth Sound Difference Contours (Future - Existing)
Note: Sound isopleth contour levels attributable only to noise produced by Wake Stone's operations (i.e. does not include
other background noise sources such as traffic noise from I-40 or aircraft noise from Raleigh Durham Airport).
29/29