20210327_N-Stewart_Noise

From:
Noral Stewart
To:
Wrenn, Brian L; Miller, David
Cc:
Patterson, Dwayne; Jean Spooner; Isabel Mattox
Subject:
[External] Review of Draft Wake Stone Triangle Quarry Acoustical Study
Date:
Saturday, March 27, 2021 8:05:11 AM
Attachments:
imaae003.Dna
Wake Stone Expansion Acoustical Study Review.pdf
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Gentlemen,
On behalf of The Mattox Law Firm and The Umstead Coalition I have prepared and attached a review
of the draft acoustical study of the Wake Stone Triangle Quarry. There are many problems with it. I
hope my comments will be helpful.
Noral D. Stewart, PhD FASA FASTM INCE-USA
Senior Principal Consultant (Part -Time)
f�:� STEWART
ACOUSTICAL
CONSULTANTS
www.sacnc.com noralsnao sacnc.com
Fax and Direct Phone Line 919-585-4486
Office Main Line: 919-858-0899 Ext 1
7330 Chapel Hill Rd, Ste 201, Raleigh, NC 27607
o��IIp�I�Op0000em

STEWART
ACOUSTICAL
CONSULTANTS
March 26, 2021
Mr. Brian Wrenn
Director - Division of Energy, Mineral and Land Resources
Mr. David Miller
State Mining Engineer
NC Department of Environmental Quality
1612 Mail Service Center
Raleigh, North Carolina 27699-1612
Phone: [phone]
7330 Chapel Hill Rd, Ste 201
Raleigh, NC 27607
www.sacnc.com
Re: Permit Application 92-10 - Comments on Noise of Wake Stone Quarry Expansion at
Umstead Park- Draft Wake Stone Triangle Quarry Expansion Acoustical Study
Dear Mr. Wrenn and Mr. Miller:
As a follow-up to my comments of July 13, 2020, 1 have been asked by my clients to review and
comment on the Draft Wake Stone Triangle Quarry Expansion Acoustical Study prepared by
WSP with a few words on the protocol on which it was based. In doing this, I have also
reviewed some documents that are part of the project file on the NC DEQ website and notes on
their concerns from my clients. My earlier comments last July provided some comments on my
background, but I have attached a brief resume.
After a brief discussion of the program protocol, I will concentrate on the draft study report
section by section skipping the Executive Summary and starting with the project description. I
will move the discussion of Blast Noise and Backup Alarms ahead of the discussion of model
results, so all model results and conclusions are considered together. Finally, I will discuss
some matters not adequately discussed in the study and make some comments.
Protocol
The protocol basically is a scope of work for the acoustical study and agreement between the
consultant and client. It is typical of such documents with a few unusual things.
It is surprising that the locations for measurements are actually set at this stage. It is not clear
how much study had been done by the consultant in identifying these locations. The description
indicates that the locations are selected "spatially cover the park to sample different noise
environments; including near the quarry, near residences, near roadways, near RDU airport,
and far away from anything where ambient noise levels could be quite low." It is not clear at all
which location fits the last criterion of where levels could be quite low. Obviously missing is any
point central to the park far from boundaries or heavy activity. It is also said about the
measurement points that "Areas in the park referred to as having "frequent human use" will get
priority, such as trails, campgrounds and picnic areas." That is somewhat contradictory to areas
"where noise levels could be quite low." Putting monitors in locations with heavy people activity
means that you wind up measuring that people activity. Also missing as a point of strong
interest would be a measurement in the park to the northeast of the "Residence" location and
northwest of the "Company Mill Trail" but much closer than "Reedy Creek Park Trail."
Member Firm - National Council of Acoustical Consultants

Wake Stone Noise Study Review Page 2 March 26, 2021
Something else glaringly missing is any reference to an effort to gather or maintain records of
weather and atmospheric conditions and quarry operations during monitoring. Atmospheric
conditions can strongly influence the sound beyond a few hundred feet from the source.
Protect Description
The simple words used to describe a project can help show the tone of what is to be expected
from the study. It is emphasized in the first paragraph that the quarry has been in operation
since 1982 giving the impression it is perhaps the older than the park, something long
established and always expected to continue to be there. However, as finally noted in the last
paragraph, the park has been open since 1934 (not 1937 as in the study and some sources),
originally a quiet retreat. The Boy Scouts owned and used a portion near where the quarry is
before it became part of the park. This paragraph describes the park as something adjacent to
the quarry, with many facilities close to the quarry's "existing facilities" giving the impression that
the park encroached on the quarry when in fact the quarry encroached with its facilities close to
the parks existing facilities. The final sentence mentions the airport runway 14-32 as an impact
on the park. However, that runway is used only by small general aviation planes and only a
small portion of them. While it has some effect on the park, the more major effect of the airport
is that of the main runways on the northernmost part of the park near the US70 entrance. That
is effectively a transition area into the main part of the park.
The project description only provides a very high-level generic description of what is happening.
For an acoustical study, the description should include some details important for consideration
in evaluating the acoustical impact. Such details are important in evaluating impact. Important
factors include the widening and increased use of a road near the park boundary, the unique
topography of the site being bisected by Crabtree Creek between the two pits requiring the
bridge and introducing the channeling of sound down the creek from the bridge area, the
relatively narrow proposed buffers between activities and the park and the relatively low berms
proposed.
The description seems to presume that the proposal will be approved (second paragraph begins
"Once Pit 2 is approved" rather than "If') Typically modern environmental evaluations consider
both "Build" and "No Build" alternatives showing the effects of each. This document seems to
presume that the quarry is something well accepted as a permanent part of the park
surroundings that will continue forever even if the proposed expansion is rejected. The
establishment of the quarry over the objections of the state parks agency, the mine regulatory
agency, and park supporters was tolerated at least with the expectation that the quarry would
have a finite life and end. In that context, this proposal to both extend the life of the operation
and add more noise to other parts of the park is particularly disturbing to the park and its users
and supporters. The proper way to define the project and scope of the evaluation is to compare
the impact of the proposal with what would occur in a "no -build" scenario that would have the
quarry operations ending much sooner.
Acoustical Terminolgy (Measurements)
The important introductory section titled "Acoustical Terminology" as written would be better
titled "Acoustical Sound Measurement Terminology." It reasonably addresses the terms
discussed but leaves out some important measurement concepts. It also leaves out a
complementary section normally present that describes important acoustical phenomena that
influence sound propagation and perception. The remainder of this section will discuss
measurement terminology and concepts. An additional section of this report will discuss sound
propagation and perception.

Wake Stone Noise Study Review Page 3 March 26, 2021
One must read between the lines to deduce that there is a basic measurable sound level that
can be measured at a point in time and plotted versus time to show variation with minimal
averaging (slow or fast response). This is the common situation in most environments and the
way the sound is actually perceived. Most of the sounds from a quarry for instance are highly
variable with time. Exceptions are certain secondary and tertiary crushers and screens which
tend to be steady. For convenience, the various other metrics discussed are often used to
analyze the data, but any of these by themselves will fail to fully show how the sound is
perceived. They must be used in combination and even then, they may not tell the full story.
The concept of frequency is introduced with octave -band and one -third -octave -band filters. It is
not made clear that such analysis of sound by frequency is essential for any calculations or
analysis for sound propagation or noise control. This is because sounds of different frequency
interact differently with various structures, environmental features, and atmospheric conditions.
All calculations must be done over a range of frequency bands and the results then combined to
establish overall levels. Typically, sounds of low frequency are less affected by various
influences and travel further than higher frequency sounds. Sometimes due to this, it is
advisable to make measurements far from a source with high -frequency sound (that is most
likely from nearby sources) filtered out and to evaluate influences based on the lower -frequency
sound only. This can be essential in North Carolina during insect season as the author realized
about 30 years ago. This methodology has now been standardized in a measurement standard
strongly advocated by the National Park Service, ANSI S12.100 Methods to Define and
Measure the Residual Sound in Protected Natural and Quiet Residential Areas. Another
frequency measurement useful in some cases is identification of specific discrete frequencies
that occur in some sounds such as warning signals.
The chart presented to illustrate sound levels requires some comment. These charts are
extremely difficult to present without the chart being misleading in some ways. While this chart
is better than some, indicating distances from sources in some cases, it still has problems.
Various sources listed can have highly variable sound levels. A person who owns a quiet
appliance would have a different perception of the appliance sound level from someone more
familiar with a noisy version of that appliance for instance.
Additional Terminology and Acoustical Effects
Any report discussing sound propagation over long distances and perceptions of sound must
introduce some concepts related to each with a little explanation as many readers will be
unaware of these factors.
The report in the discussion of modeling mentions in passing without explanation effects due to
ground effects, wind, and shielding by berms, barriers, or buildings. Not even mentioned are
the important effects of atmospheric absorption and temperature gradients. The reader needs
to know several things. Atmospheric absorption reduces higher frequency sound much more
strongly with distance than lower frequency sound. Soft ground can reduce sound over a range
of frequencies especially when the sound is originating and traveling close to the ground. When
there is a berm or barrier present, it provides benefit but causes loss of some or all the ground
effect benefit. The benefit of the berm or barrier is greatest near it, decreasing with distance.
The presence of wind or temperature variations with altitude above the ground can very strongly
influence sound levels away from the immediate vicinity of a source, reducing sound levels
upwind or when temperatures are decreasing with altitude. However, under the reverse wind
and temperature conditions much of the benefit of a berm or barrier can be lost as these
conditions cause the sound to curve downward over the berm or barrier unless it is very high.
Indeed, some texts advise against any credit for berms or barriers at distances beyond 1000
feet from the source though this is not the case if the berm or barrier is high enough.

Wake Stone Noise Study Review Page 4 March 26, 2021
Two kinds of sounds that are potential noises for different reasons. One is a non -distinctive
relatively steady sound of many frequencies over a broad range such as distant free -flowing
highway traffic and some quarry equipment such as secondary and tertiary crushers. These
sounds do not have "information content." They primarily become a noise if they are so loud
that they mask or cover up other desirable sounds but otherwise might not be noticed. In some
situations, such sound can be desirable to provide privacy. In a park setting such sound could
mask desirable natural sounds. The other type of sound typically contains information of some
sort making it distinctive. Such sounds at attention getting. They include speech, music, dog
barks, warning signals, sounds that are highly variable in level, sudden impulsive or impact
sounds, and some sounds from machinery with distinctive frequency characteristics. These
become especially objectionable when they are not sounds expected in a given environment.
Regulatory Environment
This part of the report could have been called Regulatory Environment Impact Criteria as it
discusses the selection of an evaluation criterion. The report states that the State of North
Carolina does not regulate noise but leaves it to local governments. In most quarry cases that
is correct. However, there is one aspect of quarry noise impact that is regulated by the state
and that is impact on park land of any kind. The current project must clearly satisfy the
requirement that it not have "significantly adverse effect on the purposes of a publicly owned
park, forest or recreation area". This does not require a "severe" impact, only one that is not
insignificant. There are two kinds of parks and recreation areas, those intended for quiet
activities and the enjoyment of nature and those intended for noisy activities. Thus, the same
criteria are not appropriate for each., though there is not a quantitative criterion stated. It is
unclear whether the local regulation might be applied for impact on the park in addition to the
state regulation if both the park and quarry are in the same jurisdiction.
I was involved in a support role providing measurements during the original hearings on the
quarry 40 years ago. It is my memory that the criterion used was that the average sound level
increase be not more than 3 dB at any point in the park. If that were exceeded, it would mean
that the quarry by itself would be the dominant sound source contributing more than half the
sound present. Even this would mean that the quarry would be noticeable since the sound
would be identifiable as events, but it would not be dominant. That seemed reasonable at the
time. This kind of limit is not without problems. Suppose two other neighbors also wanted to
add 3 dB to what the last had added. You could quickly wind up with a major change in the
character of the environment and a 10 dB increase. There seems to have been no effort to
consider what was discussed 40 years ago.
In search of a quantitative criterion the report lists several selected criteria without careful
examination or discussion of how they were developed or objectives. It omits other important
criteria. Many of the published criteria were developed without adequate research and
consideration. Some were developed with specific motives to reduce cost for the noise
producing government projects. Some are devised for ease of enforcement, resulting in
situations where they are either too stringent or not stringent enough.
Almost all research on appropriate criteria is government funded and typically concentrates
primarily on typical urban and suburban residential communities. The most thorough was done
in the early 70's by the EPA at the direction of Congress to devise a metric, and reasonable
criteria for noise for government programs. This resulted in the Day Night Level (DNL or symbol
Ldn) and the goal of DNL 55 for residential communities. This included a margin of 5 dB and
recognized that noise in residential areas varied with population density and would be higher in
densely populated areas. The level of 70 dBA Leq (24 hr) shown in the table is extremely
misleading as it was the criterion to prevent hearing damage.

Wake Stone Noise Study Review Page 5 March 26, 2021
Despite these findings, federal agencies set about setting regulatory goals higher. HUD initially
considered a limit of DNL 60 for their acceptable level but raised it to DNL 65 upon learning the
cost savings in developing noisier properties. The federal government has drawn a line at
around Day Night Level 65 dBA and makes strong efforts to avoid crossing that line but does so
at the expense of major noise impacts on quiet communities. It interesting that the three
branches of the US Department of Transportation (DOT) have very different approaches to
noise. All allow major changes in quiet communities because it would strongly increase the cost
of new transportation systems otherwise. The most recently developed and best thought out of
the DOT regulations is that for transit and railways. The levels quoted in the table of a 5 to 10
dB increase are for "moderate impact" for a 10 dBA increase from a 40 dBA starting point or a 5
dBA increase from a 50 dBA starting point. These are the largest permitted increases for a
moderate impact. Criteria are also given for "severe" impact. At an initial level of DNL 50, a 10
dB increase is considered severe and lesser increases are considered severe for higher initial
levels. The permitted increases for a given degree of impact decrease continuously as the
existing sound increases. They are based on a presumption that it is only important whether the
sound interferes with speech or is different from what could be found in typical residential areas.
However, importantly, this is not a criterion for locations where quiet levels are important in
themselves for the purposes of the property or expectations. The Federal Highway
Administration does set their normal level at which they consider building barriers 10 dB lower
for "Lands on which serenity and quiet are of extraordinary significance and serve an important
public need and where the preservation of those qualities is essential if the area is to continue to
serve its intended purpose." However, they do not lower this further for quiet locations as they
do with their normal criterion for residential areas. One important point about all these criteria
for transportation noise is that people who can show damages even where the government
criteria are met can recover such through legal action and such often happens.
Local city and county ordinances are typically not well written and are often copied from
ordinances of other localities spreading problems. Local ordinance requirements are typically
fixed limits based on the use or zoning of property rather than based on existing sound. They
are relatively consistent in limiting daytime sounds reaching residential areas to the range of 55
to 65 dBA with 60 dBA being by far the most common limit. Night limits are in the range of 45 to
55 dB with most either 50 or 55 dBA. The 45 dBA limit would put most residential air
conditioning systems in violation. These almost always are based on a very short measurement
period and very often allow an instantaneous measurement for which the limits are too low. The
Wake County Unified Development Ordinance limits sound reaching residentially zoned
properties to maximum slow A -weighted levels of 55 dBA daytime and 45 dBA at night (10 pm
to 7 am). The Wake County general ordinance limits the sound reaching residential properties
to 55 dBA daytime and 50 dBA night (11 pm to 7 am) based on the second highest of any 20
measurements made 10 seconds of the A -weighted slow level. Cary limits the maximum A -
weighted slow level reaching a residence to 60 dBA.
Compliance with any existing local ordinance applicable to the project is the first step for most
quarries in North Carolina. However, the case of concern here is complicated by jurisdictional
issues and noise issues on jurisdictional boundaries are common. Unfortunately, the location of
the quarry and park raises many jurisdictional issues that would need to be sorted out.
Most quarry projects in North Carolina must also obtain a special use permit. The key acoustical
factor for this beyond compliance with specific noise requirements is that the project be "in
harmony" with adjacent properties. This is not clearly defined, and courts have ruled that due to
the wording of the statute the burden of proof that the project is not in harmony is on those
objecting. Noise is clearly a factor that can be argued regarding harmony and projects have

Wake Stone Noise Study Review Page 6 March 26, 2021
been denied permits on this basis. In my experience with many quarries, the quarry developers
take steps to minimize impact on neighboring properties. This is done wherever possible with
large buffers of a few to several thousand feet created by land plots much larger than needed
for the quarry itself. There are also typically high berms around the quarry area and especially if
the buffer is not large. It is common for berms in such cases to be 40 to 50 feet high. Such high
berms are needed to intercept sound that is curving downward during temperature inversion or
downwind conditions. Sometimes, it is even necessary to enclose stationary equipment.
Several states have either statewide noise ordinances or model ordinances that local
governments must use if they wish to adopt a local ordinance. The draft report lists those of
Washington and Minnesota with the limits for residential areas, but there are many others. One
important point for Washington state is that the state can set lower limits for certain areas where
"serenity, tranquility, or quiet are an essential part of the quality of the environment and serve an
important public need." The state has also set limits as low as 39 dBA in rural residential areas.
A very important class of criteria not mentioned are those used in some states for large power
plants. Such plants are commonly located in otherwise quiet locations and are a source of
complaints where they are clearly noticed or dominant in the sound environment. North
Carolina does not have specific criteria, but the utility companies must satisfy the utility
commission. Other states have criteria that limit the increase in sound with the goal of limiting
how noticeable the plant sound is. Even where such limits do not exist, the consultants that
commonly work for the utility companies look to these criteria for guidance. Often the limit is a 5
dB increase above existing level but there is a unique way this is often evaluated that makes it
more stringent. Commonly in New England area and in some other states the existing level is
based on the L90 and the limit is based on the average level or Leq. The baseline is often the
lowest hourly L90 measured in a day or over a week, or the arithmetic average of the lowest
seven daily hourly L90 values recorded over a week. This establishes a low baseline. The limit
is then set as an hourly average level not to be exceeded that is 5 or 10 dB above this L90
baseline. This can sometimes result in a limit lower than the existing hourly average level from
other sources much of the time. In Massachusetts the limit is normally 10 dB above the L90 but
the state commonly reduces this to 5 dB for the largest projects unless the utility can prove an
undue economic burden. There are potential theoretical but unlikely circumstances where this
methodology might not work if for instance the existing sound was very steady with Leq close to
L90. This methodology has been exhaustively studied by the father and son consulting team of
George and David Hessler whose work has concentrated on power plants worldwide. They
looked not only at their own experience but surveyed other consultants. They have concluded
that this methodology works and has been accepted by their power industry clientele.
The draft study concludes its review of criteria by defining "a significantly adverse effect" as a
10 decibel or more increase in future noise levels when compared to existing noise levels." If
this were based on a comparison of the average sound level Leq to the existing L90 as in the
power industry, this could be reasonable. However, it appears to be saying a 10 dB increase in
average sound level compared to the average sound levels already being dominated in some
places by the existing quarry operations. That is a totally unacceptable criteria that would result
in a severe impact. A 10 dB increase is a dramatic change in the acoustical character of any
area. It is changing a very quiet community to a more typical one and then changing that to a
very noisy community. It must be remembered that from the perspective of the park, the
appropriate environment for comparison for any new sound should be sound without any
contribution from the quarry at all. The quarry is effectively saying that after already increasing
the sound it has bought itself a higher threshold to allow further increases. They are effectively
saying the original quarry should have been allowed to increase surrounding areas by 10 dB,

Wake Stone Noise Study Review Page 7 March 26, 2021
and now they should be allowed another 10 dB. This is illogical and unacceptable. Individual
increases by a single operation must be carefully controlled to avoid the dramatic cumulative
effect that occurs if each new project adds strongly on top of the last. The applicant has chosen
to locate the quarry in a sensitive location where it impacts not only some private landowners
but also all citizens who use the park. It has had 40 years of doing so and would be allowed
more time until the existing pit is exhausted. Any extension and expansion of activity should
demand a strong effort at noise control.
Existing Noise Measurements (Long Term)
Week-long sound measurements were made at six locations in the park, three relatively close to
the quarry or proposed expansion, and three far removed. It is not very logical to this reviewer
that fully half the monitoring locations were so far removed from the quarry area where it might
be expected that the quarry would have minimal influence. At least one more location near the
quarry in the vicinity of the locations marked R-7 and R-8 would have been highly desirable.
The location selection for the more distant locations is also very questionable. All are relatively
close to the park boundary where outside influences could be significant. None were deep
within the park at locations of minimal outside sound influence or influence by people activities.
It gives the impression they may have been intentionally selected to give high readings. Only
two of the six locations were at points with enough quarry sound to be useful in evaluating the
validity of the model. There should have been more.
The instruments used for these measurements were Larson -Davis LD720 models. These are
Type 2 instruments by virtue of the microphone used. They are Type 1 capable with an optional
Type 1 microphone. However, experience with similar instruments from this manufacturer
indicates that even with the less expensive microphone, the instruments are close to Type 1
performance up to around 10,000 Hz covering the frequencies of concern to in the study. The
report does not discuss the "noise floor" of the instruments and the influence of that on the
measurements. These instruments have a "noise floor" around 30 dBA. This means that if you
put them in a location that is actually 20 dBA, they will still report over 30 dBA. If the actual
sound level is 30 dBA and the noise floor is 30 dBA, the instrument will report 33 dBA, and if the
actual level is 40 dBA, the reported level will be around 40.5 dBA. Basically, one has to realize
that for any levels below about 40 dBA, the reported results will be high. Looking at the
reported data, there is clearly some influence at sites LT-4 and LT-6. This is not an unusually
high noise floor, but many instruments do have noise floors in the mid 20's. The major
improvement in instruments over the past 30 years in the digital era has been the addition of
more storage memory. The LID 720 has more memory than the earliest digital instruments but
not as much as more modern instruments. This limits the amount of data that can be stored
and capabilities such as recording audio samples of the sound to identify what is being
measured. It was stated that the instruments were put in trees, but no details were provided on
the height above ground, how microphones were positioned or supported, the size of the
windscreen or how far the trees were from paths where people would be walking and talking.
The measurements were made over a period of a week but in different weeks at some
locations. There is no discussion of why a one -week period was selected, of whether anything
was done to compare operations and weather during those weeks with typical conditions to
verify whether the weeks were representative, or even whether the two periods selected were
even comparable to one another. What is one had all wind from the northeast and the other all
wind from the southwest. Sound could have been very different. There is no mention of any
records of weather or quarry operation conditions or any attempt to evaluate whether the
monitored periods were representative, or even whether the sites measured different weeks
could with validity be compared with each other.

Wake Stone Noise Study Review Page 8 March 26, 2021
Records on weather should be kept or obtained during measurements (especially wind
direction, high wind speeds, sunrise and sunset times, clear or cloudy skies, and rain) and
source operating conditions for the monitored period. These factors can then be compared with
the sound observed at various times for influences. For instance, more sound influence from
the quarry would be expected in the park with winds from the southwest than when winds are
from the northeast. Without knowledge of that the data are meaningless especially if the wind
happened to be predominantly from the northeast. Sound around and for a while after sunrise
will be louder than later in the morning and afternoon. With the most common 4- inch
windscreen, a wind of around 12 mph can cause the microphone to register between 40 and 45
dBA due to the wind blowing over the windscreen. A wind of 24 mph can cause levels of 55
dBA or greater to be registered when they do not exist. A smaller windscreen such as is
provided with the LD 720 meter would give higher results. Fortunately, historical hourly weather
observations at the airport are available online at wunderground.com and possibly other sites.
This information should be reviewed hour by hour with the sound data for influences.
While much data was obtained, only limited data are presented. The first presentation is a table
showing workday averaged sound levels at the six locations under three activity conditions:
normal workday, maintenance time, and Sunday with no work. Results are rounded to an
integer dB which can be misleading when differences are small such that a difference of almost
zero and almost 2 dB could potentially look like a one dB difference. This is seen in the
difference results to the right in the table that do not match the apparent differences when one
simply looks at the levels listed. It is clear that the locations selected away from the quarry area
were places influenced by local nearby activities that also decreased on Sunday. A nearby
resident reported that a home was under construction near the Sendaro gate during the
monitoring period. Though it is not said, perhaps the intention was to show sound at other
places around the perimeter of the park comparable to that near the quarry. However, for over
40 years before the arrival of the quarry, this area near the creek was prime park area away
from the more developed perimeter and developed by the park as such. The question is
whether the intrusion of the quarry in that area has had an influence on it and would the
approval of the proposal delay recovery of that area and spread noise to other areas.
The second presentation of the weeklong data is a single plot for each site with all the data for
the week averaged, presumably including Sunday. This hides variations from day to day that
could have been influenced by weather. High levels on one or two days could have possibly
strongly influenced the results. Data for the individual days should at least be available as an
appendix, and it should be looked at along with weather and quarry operational data to try to
correlate the sound with sources. If there is for instance a pattern on a given day with several
monitors having maximums in the same hours, that would tend to indicate the same source
affecting them. If patterns are different everywhere, it is more of an indication of local source
dominance. Ideally there would be data with a finer resolution of say one -minute Leq values
and even some sampling audio recordings. The memory limitations in the instruments
prevented at least the audio recordings. A check of the weather records shows that on all but
one of the monitored mornings, the temperature reached minimum and started rising around 9
am. Sunrise was around 7 am. Note the consistent hump in the sound data from around 5 to 9
am. That is a result of a strong temperature inversion during that time that is going away
starting around 9 am. During that period sound from many distant sources carries more
strongly with those upwind from the observer location being strongest. It appears that
something was possibly happening near location 4 at around 9 am on most mornings or very
strongly on one morning. The data for various days could be compared with wind direction and
speed information for potential effects.

Wake Stone Noise Study Review Page 9 March 26, 2021
Before some final discussion of this long-term data, I must pause to issue my complaint about
the formatting of the plots that made it difficult for me and at least one of my staff members to
interpret the data. I have created many plots similar to these. They typically include most of the
following but not all: Lmax, L1, L10, Leq, L50, L90 and Lmin. Now, of all these, all except Leq
will always fall in that order from top to bottom without crossing. These except Leq do not have
to be distinguished by different colors or line styles or markers to be clear what they are as long
as you know which ones are plotted. Leq is the exception. It will be mostly between L50 and
L10, but can easily cross L10 and in rare cases cross L50. Thus, Leq must be very clearly
distinguished from L50 and L10. I typically make the Leq line much heavier than the others or
use a different line style for it. If colors are used, one must NEVER depend on the colors as the
only way to distinguish the lines. A significant part of the population cannot distinguish all colors
and some people will sometimes make black and white copies. I could not tell the difference
between the Leq and L10 lines and had to get help because they cross in some cases.
Now back to the data. I strongly encourage the plotting of L50 in addition to Leq. The Leq is
strongly influenced by brief loud events and is not representative of the sound present most of
the time. The L50 gives an indication of the level where the sound is above and below it half the
time. Note that in several cases the Leq goes above the L10. In those cases, there are loud
events of short duration, lasting less than 10% of the hour, but loud enough to drive up the Leq
to greater than that level exceeded 10% of the hour. These will be cases where the Leq is also
well above the L50. Thus, I strongly recommend adding the L50 to these plots.
Existing Noise Measurements (Short Term)
Short-term (15 minute) measurements were made with a Svantek 971 instrument, a more
modern meter with Type 1 precision, more memory than earlier instruments and ability to record
audio for listening. The stated purpose of these measurements was "to positively identify and
correlate audible noise sources with the sound levels being measured." Actually, based on a
later statement in the modeling section, some measurements were also made near specific
sound sources as data for input into the model. In any case, such measurements should have
been made even when other data was available for modeling just to verify the validity of such
data. Another good use of short-term measurements is to supplement the long-term
measurements with synchronized measurements at additional locations. Such combined with
the long-term measurements would allow estimates of long-term results at additional locations.
However, there is no indication this was done.
Some data from short-term measurements is presented in Table 3. However, it is totally unclear
what the data in the table represents. Is it a sample of four short-term measurements at four
locations at undisclosed times and with not discussion of what was happening during those
specific measurements? Is it an average of several (undisclosed number) of short-term
measurements at the four locations? We are not told clearly. When were the measurements
made? What were the actual locations? How many measurements were made? (Only a few
seem to be discussed.) The locations are not marked on a map. Short-term results can vary
widely with exact location and time. Without further explanation, the data of Table 3 are
useless.
We are told that while in the park the observers had difficulty distinguishing the quarry sound
from road sound, which is probably the case for non -distinctive quarry sound far enough from
the quarry, though the quarry is adding to the sound. Distinctive sounds noted clearly from the
quarry included back-up alarms, blasting, and sirens before and after the blasting. It was noted
that the siren after the blasting lasted for a minute and that the blast could be felt as well as
heard.

Wake Stone Noise Study Review Page 10 March 26, 2021
Some measurements of a blast are discussed and compared with an aircraft overflight. This
discussion shows that there must have been multiple Svantek 971 instruments in use since
some simultaneous measurements were made. It is not reported if further simultaneous
measurements were made. During these measurements including the blast, the data was
stored in samples of 1 second Leq or 1 second average levels, A -weighted. It is not explained,
but the resulting maximum 1 second Leq level from the blast is approximately equal to the A -
weighted Lmax with slow response. This is not the standard way of reporting blast levels. For a
sudden sound like the blast the slow maximum level will be significantly less than the fast
maximum level which is more representative of ear perception. This one -second maximum
level is compared to similar one -second maximum levels for aircraft where the sound has a
gradual slowly increasing level. That is not an appropriate comparison. See the discussion of
this in the "Blast Noise" discussion later. For the brief time it occurs, the ear will perceive the
suddenly occurring blast as a more significant event than a single aircraft flyover. There is no
discussion of the type of aircraft and whether they were directly overhead or off to the side. It is
somewhat disturbing that it is reported that the measurement of this one blast was used to
estimate the sound power of a blast for modeling. Blast can vary significantly from one to
another, and atmospheric conditions can influence the recorded level beyond a few hundred
feet from the blast. It is common practice at quarries to try to avoid blasting during temperature
inversion conditions. A measurement during temperature lapse conditions (decreasing
temperature with altitude), unless within just a few hundred feet and in a location with a clear
line of sight, is totally unreliable for estimating the sound power of a blast. Quarries are required
to maintain records of ground vibration and peak sound level for all blasts at a location. The
blast management companies should have much data on blasting.
Noise Prediction Model
The Cadna-A computer program implementing the ISO 9613 calculation methodology was used
for modeling. Cadna-A is one of few other programs that provide multiple ways of calculating
sound propagation with ISO 9613 being one. Other calculation methods have been devised
sometimes for specific types of sources such as highways or airports, and even quarries. Some
countries or government agencies require the use of specific calculation methods. ISO 9613 is
the most widely used method when another is not required. The implementation of ISO 9613 in
different computer programs may give slightly different results. However, the data input into the
program to describe source sound output and the environment can have more significant effect.
There is concern that it is said that the source sound data for some sources was input as only
an A -weighted value rather than octave -band or one -third -octave -band data. When only A -
weighted levels are input, the program has to effectively make assumptions about the frequency
content of the source which may not be correct.
It should be emphasized early in this discussion that the model is calculating an hourly average
level which does not show variation of sound levels with time and maximum observed event
sound levels. This is mentioned later but the significance could be overlooked.
The report says modeling assumed simultaneous operation of all noise producing equipment as
a worst -case assumption. This should be explained further. Later in the discussion there is
mention that "usage factors" were developed for some equipment and applied. That is
reasonable and more realistic. How were moving vehicles distributed with location? They could
all be put in the model operating, but in a location where they introduce the least noise in places
of concern. Has equipment that would never actually operate simultaneously been assumed to
be operating simultaneously? Usage factors could account for that.

Wake Stone Noise Study Review Page 11 March 26, 2021
The ISO 9613 calculation method uses "ground factors" with values ranging from 0 to 1 in
calculating ground effects. Soft ground that includes most ground covered with vegetation has
a value of 1. Areas of pavement, water surface and very hard ground without vegetation have a
ground factor of 0. The method allows intermediate values where the ground surface might be
mixed or something intermediate between the hard and soft surfaces. A value of .5 was
reported to be used for the quarry area. That needs some discussion and justification. Many of
the surfaces in and around the quarry are actually very hard. A value of .5 is questionable
without further justification.
It is reported that ISO 9613 assumes a mild wind blowing in the direction from each source to
each calculated receptor location. It also assumes a mild temperature inversion. This is
necessary as results are not so easily calculated otherwise. Levels could be significantly lower
during temperature lapse conditions or at upwind locations. In the real world when there is
wind, the levels would be reduced in the upwind direction. With stronger winds or inversion,
levels could be higher especially downwind. The assumed conditions give an approximate
representation of average conditions. There can be periods when an unstable atmosphere can
cause focusing and significant increase of sound downwind, with the locations typically moving
so the effect is brief a particular location. Such is always ignored as an act of nature.
The conditions modeled and data used are further discussed. The most confusing matter is the
source of the equipment sound power data used. The discussion first says data were based on
measurements made on site. It then says data from technical literature the highway
administrations road construction model was used. So, which was it? It was probably some of
both, but some explanation is needed.
Blasting Noise
I would agree that in many cases blasting is not nearly the problem it is made out to be. In
many cases I have looked at, there was sufficient distance between the blasting and potentially
affected neighbors that I have not considered it significant compared to other concerns.
However, I have significant concern in this case due to the close proximity of the blasting to
neighboring properties and the predicted strong increases in blasting sound.
I do not accept the idea of computing blast levels as A -weighted slow maximum results. It is
well recognized that this is an inappropriate way to evaluate blast sound and I know of no
criteria to evaluate blast based on this metric.
North Carolina like most states has requirements for maximum allowed ground vibration and
peak overpressure which is the basis of a peak unweighted sound level. Peak sound level is a
much more widely used methodology for blasts. The state criteria are based more on the
prevention of structural damage than on the protection of the acoustical environment. The
current limit is 129 to 134 dB Peak depending on the lowest frequency included. The applicant
must demonstrate compliance with these requirements as a minimum. The US military uses
peak level as a criterion for individual blasts around military. The military realizes that blasts
vary in themselves and with weather. Thus, they consider the variation and use the blast level
exceeded by 15% of the blasts in their evaluation. The goal is to keep 85% of the blasts below
115 dB for a low risk of complaints and below 130 dB for a moderate risk of complaints based
on typical expectations around such bases. If as many as 15% are over 130 dB a high risk of
complaints exists. However, importantly this is for communities near military bases, not parks.
The ANSI standard S12.9 Part 4 recommends measuring individual blasts using the C-weighted
sound exposure level (CSEL) which gives a result very close to the maximum slow C-weighted
level. It then recommends where there are a large number of blasts per day, this result should
be adjusted by a formula in the standard, and then that result should be entered into

Wake Stone Noise Study Review Page 12 March 26, 2021
calculations of long-term average levels. A number per day is not given, but a 1981 EPA draft
document suggests 8 or more. When there are fewer as in a quarry situation, the individual
blast will have an insignificant effect on the long-term average and must be evaluated
individually. A limited search has not revealed appropriate criteria for such individual events.
However, the research for the adjustment factor for the CSEL sheds some light and also shows
the relationship between SEL for aircraft and blasting. A blast with a CSEL of around 103 dB is
found to equally annoying to an aircraft or non -impulsive event of ASEL 103 dB. For lower SEL
values the blast C weighted is less annoying than the aircraft. For higher SEL values, the blast
is more annoying. A limited search has not found criteria for individual events based on CSEL
as most research has concentrated on situations with many events per day.
Though the A -weighted maximum is not an accepted way to evaluated blast noise, the
information provided in the report does raise strong concern. The calculated results show
extreme increases in blast levels at the nearest residence and Foxcroft Lake, very strong
increases at Reedy Creek Park Trail and somewhat surprisingly at the picnic grounds and the
residences near Trenton Road to the east and clearly noticeable increases almost everywhere.
Though not clearly explained, this could partially be due to the existing blasting now being deep
into the pit. Even after the new pit reaches a low level, the blasting down in that pit is still
predicted to be clearly noticeably louder than current blasting. This is a serious concern to be
carefully evaluated. The current study is a very weak effort at looking at this issue.
Backup Alarms
It is encouraging that the proponent is agreeing to take some steps to reduce backup alarm
sound. Traditional alarms have tones around 1200 Hz which propagate strongly enough to be
heard over long distances due to their strong tonal concentration though their overall level may
not significantly affect overall sound levels. This creates a problem not only for neighbors but
also for worker safety. There are so many alarms sounding that can be heard that it is hard for
a worker to know when they are really in danger. This leads to people ignoring the alarms. The
new type of alarm discussed not only reduces the sound propagation to neighbors but also
gives workers a clearer indication that they are in danger.
Even if the quarry operator equips all their equipment with quieter and better alarms, there is still
an alarm problem to deal with. There will be many trucks on the quarry site not under the
control of operator. These will be customers coming to pick up product, trucks coming to take
away overburden, and possibly even trucks under contract to haul on the site. This problem
needs to be address through traffic pattern control, arranging the travel paths of these off -site
trucks to at least minimize if not eliminate backing.
Noise Model Results including Sound Isopleth Contours
Results from the modeling are first presented for eight specific discrete locations, the six long-
term monitoring locations plus two more added at the request of DEMLR where long-term
monitoring should have been conducted. It is not clear whether these two additional points are
on park property, but it is assumed they are. (A statement is again made about all equipment
operating simultaneously without consideration of the "usage factors" that were discussed.)
Before getting into further discussion of results, it is at this point in the report that the data used
to calculate highway noise is discussed. It is said that the traffic data used was "noted during
field measurements" with no further explanation. It should be known that NC DOT has a
counting station at this location on 1-40 and that the percentage of heavy trucks at this point is
extremely low for an interstate highway. It is also not made clear whether this traffic noise was
computed with or without the new pit, which would influence the traffic noise due to replacement
of soft ground with hard surface at lower elevation in the new pit area. This also shows results
were calculated without the quarry operating, but contours are not presented.

Wake Stone Noise Study Review Page 13 March 26, 2021
Later in the report, the calculated sound contours are presented. It is strange that the contours
are not discussed as part of the results. The two sets of basic contours presented are not
labeled clearly, are to a small scale in the areas of greatest concern, and do not clearly show
park the boundary between park and quarry and identifiable park locations. A third contour map
shows the difference between the other two contour maps but uses opaque colors making it
impossible to identify the quarry/park boundary or other landmarks.
A staff member with better color vision has identified the contours shown on the next two pages.
For the colors that I can see with the very small color identification bars, it appears to me that
the labels match the identification bars. Colors are not identified for the two outermost contours.
Even to my staff member with good color vision, those two contours look like possibly the same
color. It is possible that they are both 30 dB contours, but not likely. I have identified the
outmost one as " 257'.
Next, I did something that anyone presenting such data as contours and as calculated results
should do to preserve credibility in the results. I compared tabulated results for specific
identified points with the result read from the contour for each point. I must point out that you
never expect to get exactly the same result for every point when you do this. Contours will have
a little error due to the way the curves are smoothed between calculated points. Below is the
comparison assuming the outmost contour is 25 dB. The differences are too great not to raise
questions. What can be the problem? It may be as simple as not indicating the calculation and
measurement points precisely on the maps. However, this must be resolved.
Comparison of tabulated and contour results
Location
Existing
Difference
Prod 280
Difference
Table/Contour
Table/Contour
R1 (LT3)
46/40
6
49/50
-1
R2 (LT2)
50/46
4
52/48
4
R3 (LT1)
52/46
6
52/46.5
5.5
R4 (LT5)
35/29
6
35/30
5
R5 (LT4)
37/32.5
4.5
35/33.5
1.5
R6 (LT6)
31/24
7
31/25
6
R7
50/46
4
53/50
3
R8
48/45
3
50/49
1
One might expect that possibly with the movement of the pit activity there would be reduction of
noise in some areas to go along with increase in others. However, that does not appear to be
the case. There are only increases in noise with extension of that noise far into the future. The
trucking activity to move the rock to the existing plant appears to be more than the mining
activity down in the existing pit. If one thinks about it, moving much of the transport activity from
down in the pit to the newly widened high road near the park would logically do that.
Conclusions of the Draft Study
The draft report draws conclusions which should not be considered until the questions about the
results raised above are resolved. However, even more important is the methodology and logic
by which the impact of the proposal is evaluated. The consultant is presuming that the baseline
for evaluation is existing conditions. If the baseline was no existing quarry and a proposed new

Wake Stone Noise Study Review Page 14
March 26, 2021
quarry, that might be logical. However, using the current quarry noise as a baseline is
presuming those conditions always existed in the memory of anyone alive and would always
continue to exist into the long foreseeable future. From the perspective of the park and park
users, the appropriate baseline for comparison is the existing condition that existed for the first
47 years of the park and which would exist again after the completion of the life of the existing
pit. What is going to happen when the new pit is depleted? Is there anything to prevent another
action to move further west into the "bicycle park" or other area. This was never a reasonable
site for a quarry, immediately adjacent to a park of this nature without room to leave a
reasonable buffer and put adequate berms on such buffer.
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Wake Stone Noise Study Review Page 15 March 26, 2021
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Future Condition Contours
Concluding Remark and Additional Concerns not Addressed
This was a very disappointing report. It missed a golden opportunity to demonstrate a
commitment to noise control to the extent possible given site constraints to justify the privilege
of continued and expanded operations. Clearly the scope was constrained though perhaps
some work was not reported.
The existing quarry was granted a permit with requirements for noise control 40 years ago and
the quarry has been operating since with some impact on the park. One would expect that any
effort to continue and expand operations would begin with a strong report of all the efforts at
noise control over that period, both showing compliance with the original requirements with
illustrations and examples of additional steps taken as technology has changed over time.
The evaluation of the blasting appears not to have been given very serious attention.

Wake Stone Noise Study Review Page 16 March 26, 2021
With limited monitoring sites the sites were poorly selected. It appears that the areas of
greatest concern to the park were not identified or were ignored in selecting locations. some
significant short-term hour-long measurement synchronized in time with the other monitors
would have helped. There is no evidence this was done. There was inadequate investigation of
the operations and weather during the measurements. Very limited data was presented.
As noted in the discussion of traffic data and analysis, results were computed without the quarry
operating to obtain traffic results, but no contours of this condition were presented. Perhaps this
was due to concern it would show what the quarry is adding clearly. It is not known if the traffic
only noise was computed both with and without the new pit. That could show the adverse effect
of hard quarry surfaces at lower elevation replacing removed soft ground at higher elevation on
the transmission of highway noise into the park. There are several factors regarding the
modeling that was done that are not adequately explained. The contours were apparently not
carefully checked against point calculations. The contours are not clearly labeled or presented
in a way that makes it easy to see where they are in the park and other areas.
The topography of the area plays a strong role in the spread of sound and the difficulty of noise
control. The creek through the site creates a channel for propagation of sound from the bridge
and eliminates the possibility of a continuous berm or barrier between the quarry and park. This
was not discussed. The area to the north of the expansion area is very important to the park
and parts of it are at higher elevation. The plan is to put a minimal berm in that area though
interrupted by the lake and creek. The park is very concerned that the low berm might not even
break the line of sight between the high areas and the Pit 2 area, much less be high enough to
be beneficial during downwind and inversion conditions. There is also a clear line of sight from
the high area to the bridge over the creek. With no barrier between the activity and Foxcroft
lake, the lake water surface could create a hot spot of sound north of it. It is hard to evaluate
whether the model catches these effects with the way the results are presented.
Clearly the scope of the consultant was limited to modeling and considering only what was on
the plans with no effort to assist with improved noise control. Once the model is set up, it could
have been easily run with and without the berm and with different berm heights to evaluate
effects. The park supporters have expressed strong concern about the narrow buffer between
the park and quarry in this area. A higher berm can strongly help make up for a narrow buffer.
There will be excess overburden providing much material for a higher berm. However, the berm
height is probably limited by another factor. This site is constrained between the park and
highway. A berm needs a footprint width at least twice its height. Thus, a higher berm would
reduce the area that could be mined, probably why the buffer is so narrow also.
Perhaps the thing that most shows the lack of concern is the assertion of a right to add to the
noise already put into the park an amount of sound that is ten times as much. That is what a 10
dB increase amounts to. This would not just be noticeable; it would totally dominate the
environment. If the 10 dB increase were only near the boundary, there would still be a strong
increase over much of the park. While is does not appear they intend to do this, just the idea of
asserting such a right shows a total lack of concern.
Sincerely,
STEWART ACOUSTICAL CONSULTANTS
Noral D. Stewart, PhD FASA FASTM INCE
Cc: Dr. Jean Spooner, Umstead Coalition, Ms. Isabel Mattox, Mattox Law Firm
Mr. Dwayne Patterson, NC Division of Parks and Recreation

STEWART
ACOUSTICAL
CONSULTANTS
Noral D. Stewart
Senior Principal Consultant
Phone: [phone]
7330 Chapel Hill Rd, Ste 201
Raleigh, NC 27607
www.sacnc.com
Education: BSME (with honors) - 1969, MSME - 1974, PhD — 1981
Department of Mechanical & Aerospace Engineering, North Carolina State University at Raleigh
Specialization in acoustics and noise control at all levels
Honors and Recognitions: INCE - Laymon Miller Medal for Excellence in Acoustical Consulting
Fellow of the Acoustical Society of America Award of Merit- Fellow of ASTM International
NCSU Mechanical and Aerospace Engineering - Hall of Fame - 2013 Inaugural Class
ASTM E33 Wallace Waterfall Award Phi Kappa Phi Tau Beta Pi Pi Tau Sigma
Technical and Professional Society Membership and Activities
National Council of Acoustical Consultants — NCAC Principal
President - 00-02, Pres. Elect 98-00, VP 96-98, Board of Directors 94-04
Bylaws Chair 05-current Long -Range Planning Committee - 00-Life, Chair 02-04
Acoustical Society of America - Fellow
Member - Technical Committee on Architectural Acoustics 96-20
Member - Technical Committee on Noise 95-10, 11-18
North Carolina Chapter Chair 79-80, Sec -Treasurer 77-79, 83-91, Treasurer 91-96
Institute of Noise Control Engineering - Member
Co -Chairman - 1981 INCE National Conference - NOISE-CON81
Papers review for Noise Control Engineering Journal
ASME International — Life Member
Papers review for various technical divisions
Standards Activities
ASTM International Committee E33 on Building and Environmental Acoustics
Vice Chair - 04-09, 12-17 - Chair — Subcommittee E33.05 on Research 11 —
Chair - Task Groups for standards E336, E1686, E557, E1332, and E2964
Acoustics Proposal Review Committee of Facilities Guideline Institute (Medical Facilities) 2015 -
ASA-ANSI Committee S12 Working Group on Classroom Acoustics Standard S12.60
Consulting Experience: Consulting since 1977, Full time 1981-2016.
Consulting activities have covered the broad spectrum of problems involved in architectural
acoustics, community and environmental noise, and industrial noise control. Largest acoustical
consulting firm headquartered in the area between Washington, DC and Atlanta, GA.
Expert Witness: Over 30 cases in Federal and state courts of NC, SC, & TN, and in arbitration.
Publications and Presentations:
Co -Author of chapter on Community Noise in the AIHA Noise Manual
Six Refereed Journal Papers Eight papers in Proceedings and Magazines
Nineteen Invited and Ten Contributed Presentations at National & International Conferences
Primary Author of Two ASTM standards and major revisions of another
Ten training classes including national teleconference on Community Noise for ASHA
Thirty Presentations to Regional Organizations
Special Invited Activities:
Co -Editor of Proceedings and Co -Chair of Noise -Con 81 National Noise Control Conference
Principal Noise Control Expert 1990 NIH Consensus Conference on Noise and Hearing Loss
Represented all major acoustical organizations before International Codes Council 2011
Invited by National Academies of Engineering to discuss future of industrial noise control in 2014
Member Firm — National Council of Acoustical Consultants