2 - Combined Response to ADI 4

May 24, 2021 ADI Letter #4
Noise impacts near Foxcroft Lake and Dunn residence, additional mitigation, and buffer clarification
1. In your report, "Wake Stone Triangle Quarry Expansion Acoustical Study," on page 28, Figure 14
shows an isopleth depicting the sound increase between existing and future conditions. The
greatest noise impacts off the property occur across Foxcroft Lake and at the Dunn residence.
Based on Figure 14, there is concern that the noise from the quarrying operation may have an
impact on the Park. The Division understands that the isopleths in Figure 14 were developed
using conservative modeling and did not take into consideration vegetation.
It is important to note that the isopleths illustrated in Figure 14 of the "Wake Stone Triangle
Quarry Expansion Acoustical Study" depict only the Cadna-A Model suggested potential increase
of quarry -related noise by comparing modeled future quarry noise levels to modeled noise levels
attributable to present day quarry activities. It does not represent an increase between existing
and future conditions for all noise sources, including airport and interstate highway noise.
A. Please supply a written explanation as to how the current vegetation on the east side of
Foxcroft Lake would affect the noise impact that is being shown in Figure 14. In addition,
please propose other mitigating devices needed to reduce the noise impacts on the east side
of Foxcroft Lake.
The attached memo from Erich Thalheimer (WSP) dated August 9, 2021, addresses the effects
existing vegetation on the east side of Foxcroft Lake might have on quarry noises experienced
in Umstead State Park. This vegetation will primarily provide a visual screen of proposed
future quarry activities from the small area of concern northeast of the lake.
The Cadna-A noise model indicated that the dominant source of quarry noise in this area was
anticipated to be from the proposed use of the existing perimeter road on the north side of
the existing quarry pit (Pit 1). To lessen the effects of this model -suggested noise increase on
that small section of Umstead State Park immediately northeast of Foxcroft Lake, WSC
directed WSP to examine additional mitigation measures that we might employ. Various
sound barrier walls were considered and modeled at different locations and heights to
achieve a reduction in modeled noise. For the area northeast of Foxcroft Lake, the most
effective (and only practicable) additional mitigation was the inclusion of a sound barrier wall
along the north side of the existing Triangle Quarry perimeter haul road and across the
proposed bridge. Modeling of a 12-foot barrier wall was enough to eliminate the haul route
as the dominant source of noise for the area. However, to also function effectively as a visual
barrier and to be consistent with the noise barriers previously proposed along the northeast
sections of this haul road, Wake Stone will construct a 14-foot acoustical barrier wall as
illustrated on the Wake Stone Site Plan set revised August 4, 2021.

B. The Dunn residence seems to be an area of offsite high noise level increase. Please provide
either additional enhanced mitigation to the proposed plan or supply a written explanation
as to how the proposed mitigation measures will adequately protect the Dunn residence.
The attached memo from Erich Thalheimer (WSP) dated August 9, 2021, also addresses the
noise concerns for the Dunn residence. Wake Stone maintains that a significantly adverse
effect in terms of quarry related noise would be defined as a 10-decibel increase in noise
attributable to quarry activities. Furthermore, a significantly adverse effect to a private
residence is not a denial criterion. However, Wake Stone strives to minimize the impact of
quarry operations to all its neighbors.
In response to the DEMLR request to re-examine the model predicted noise levels at the Dunn
residence, Wake Stone explored many options, including Cadna-A model runs to ascertain
berm height that would be required to yield any significant reduction in modeled noise levels.
Through that effort it was determined that placement of a sufficiently high berm was
impractical. As another possible solution, Wake Stone examined the potential use of "sound
walls" such as employed along public highway rights -of -way and in certain industrial
applications. Through several iterations of modeling, a wall design varying from 16-24 feet
high was determined to provide an acceptable reduction in modeled noise levels at the Dunn
residence. Although construction of such a wall will result in significant additional site
development costs to Wake Stone, we are proposing to replace much of the originally planned
security fence and vegetated earthen berm with such an engineered sound wall. These
proposed changes are illustrated on the attached "Proposed Additional Noise Mitigation"
schematic, and on the Wake Stone Site Plan set last revised August 4, 2021. These drawings
illustrate the location and height of the two different walls, as modeled by WSP. The originally
proposed security fence will still be utilized along Interstate Highway 40, and from the eastern
end of the wall to Crabtree Creek to minimize land disturbance in those areas. In addition to
providing improved noise reduction, site security, and visual barriers as compared to the
previously proposed security fence, vegetated earthen berm, and 100' unexcavated buffers,
Wake Stone believes that a decorative "DOT -style" noise barrier wall also has the following
advantages:
• The area of initial land disturbance (particularly along Old Reedy Creek Road) will be
significantly reduced.
• The time needed to construct a sound wall will be significantly less than the time to
construct an earthen berm (weeks versus months), and significant volumes of dirt will
not need to be hauled to the construction area.
• A decorative (formed panel) sound wall barrier would be much more esthetically
pleasing than the chain -link and barbed wire security fence, especially in high visibility
areas such as along the Old Reedy Creek Road public thoroughfare.
• Although it will require a significant up -front capital investment by Wake Stone to
construct a decorative formed panel wall, these costs will be offset by recovery of
additional reserves made available in portions of the area previously designated for
berm construction.

2. Please clarify whether the area around Foxcroft Lake, outside of the 50' wetland buffer, is to be
considered a designated undisturbed buffer. Please label and indicate on the mine maps any
additional designated undisturbed buffers around Foxcroft lake, including type and size of the
buffer.
No areas around Foxcroft Lake are currently proposed as "designated undisturbed buffer" other
than the mining permit -stipulated stream/wetland buffers and Neuse River Riparian Buffer Rule
riparian buffers. However, no land disturbing activities are currently planned east of Foxcroft
Lake. Ingress -egress via existing trails, and travel over open forest floor, will be used to access
this area for construction and maintenance of the security fence. Wake Stone does not intend to
clear any trees except as needed to construct and maintain the security fence between Foxcroft
Lake and the easternmost property boundary. However, the need to continue to maintain this
security fence for the life of the operation prevents designating this entire area as "undisturbed
buffer." Wake Stone cannot and will not engage in any land disturbing activity beyond the limits
of disturbance as illustrated in the attached Site Plans and Erosion and Sediment Control Plan
without the approval of the Division of Energy, Mineral, and Land Resources.

WSP USA, Inc.
100 Summer Street
Boston, MA 02111
(617) 426 - 7330
www.wsp.com/en-US
MEMORANDUM
To:
Sam Bratton (Wake Stone)
From:
Erich Thalheimer (WSP)
Date:
August 9, 2021
Project Name:
Wake Stone Quarry Noise
Project Number:
31402799.000
Subject:
Responses to DEMLR ADI Noise Questions 5124121
This memo is intended to respond to ADI questions from DEMLR dated 5-24-21 regarding concerns of
increased noise at the area of Umstead State Park east of Foxcroft Lake and at the Dunn residence adjoining
the proposed Pit 2 expansion area. An updated sound isopleth graphic is also included, as requested, to
supersede Figure 14 in our (WSP's) original report dated 3/12/21.
Responses to Question 1:
A. Existing dense vegetation will remain in the area east of Foxcroft Lake. The benefit of this buffer
is primarily visual. The benefit of vegetation for noise attenuation is only significant over longer
distances. Therefore, there may be a benefit to areas further inside the park from this
undisturbed forested area, but at the location described in this request, i.e. at or near the property
line, the vegetation would not play a significant role in reducing the modeled noise levels. For
this reason, we did not include vegetation in our noise model in order to be conservative. With
our assistance, Wake Stone has examined the feasibility of multiple additional mitigation options,
as follows:
Option 1 was the potential placement of a noise barrier (wall or curtain) at or
along the proposed security fence between Foxcroft Lake and the eastern
property corner at Crabtree Creek. Unfortunately, additional acoustical modeling
showed that to achieve any appreciable reduction in noise, this barrier would
have to be taller than the proposed 8' security fence. Given that constraint, any
additional noise barrier would likely require significant land disturbing activity,
would constitute a financial hardship for Wake Stone, and would potentially
reduce the effectiveness of this forested area as a visual buffer.
ii. Option 2 was the potential placement of a noise barrier wall along the existing
quarry perimeter (haul) road and the proposed bridge. This haul road noise
source was identified in our models as the dominant source of noise likely to
affect the area of concern. Modeling of this mitigation measure indicated that such
a barrier would remove this road as the dominant noise source and provide
approximately 1 decibel noise reduction at the small area of concern northeast of
Foxcroft Lake. However, with the removal of the perimeter road as the dominant
noise source, the Pit 2 expansion area is then expected to become the dominant
source (see Option 3).
iii. Option 3 was the potential placement of a noise barrier along the western
boundary of Foxcroft Lake to further mitigate potential noise from Pit 2.
Unfortunately, due to topography, placement of a noise barrier at the outer
extents of the proposed pit area would be impracticable and unacceptably costly
due to the required height of the barrier and the length of the barrier needed to
provide minimal reduction in noise. Construction of such a barrier also has the
potential to greatly complicate Wake Stone's grading and site development plan.
114

It is also important to keep in mind that the noise from Pit 2 will diminish over
time as the equipment is moved to lower elevations as the site is developed.
Ultimately, the only additional noise mitigation measures that are practicable for Wake Stone to propose
included (1) erecting a substantial noise barrier wall along the Dunn property, the northern side of Pit 2, and
along Old Reedy Creek Road, in lieu of the previously proposed earthen berm, and (2) a 12 foot tall noise
barrier along the end of the haul road and associated bridge to reduce noise affecting the Foxcroft Lake area.
Updated Figure 14 (below) shows the modeled sound isopleth contours with this additional mitigation.
B. The Dunn residence was also raised as an area of concern for increased noise. WSP contends that
the only statutory requirement for residential neighbors is that the operation will not "constitute
a direct and substantial physical hazard." The modeled noise levels do not come anywhere close
to posing a "physical hazard" associated with hearing conservation or loss. Nevertheless, Wake
Stone had attempted to minimize noise concerns at the Dunn residence by previously proposing
an earthen berm, the tallest section of which was around the Dunn property. Additional
mitigation measures were explored and modeled by WSP to evaluate their efficacy. However,
due to the location of the Dunn's house being uphill from the proposed Pit 2 expansion area, it
was determined that the height of an earthen berm needed to reduce the modeled noise levels by
just 1 to 2 decibels was unacceptably tall, would increase the footprint of disturbed land area
required, and would increase the time it would take to construct such a berm. That led Wake
Stone to examine the feasibility of a DOT -style sound wall, made of concrete panels or equivalent,
which presented a host of improvements over the previously proposed earthen berm:
i. The area of land disturbance required for construction would be significantly less
with a sound wall than that needed for an earthen berm.
ii. The time needed to construct a sound wall would be several weeks rather than
several months for an earthen berm.
iii. The height of a sound wall could be easily varied to provide optimum noise
reduction for neighboring properties.
iv. A more decorative (formed panel) concrete sound wall barrier could replace the
security fence along the majority of the perimeter, thus providing security as well
as a visual and noise barrier.
v. The area that was proposed for the earthen berm would be available for Pit 2
development which would increase the stone reserves available to Wake Stone.
This would allow Wake Stone to eventually recoup the high cost of this initial
investment for the noise wall.
Consequently, Wake Stone is proposing replacing the previously proposed security fence and earthen berm
with a decorative DOT -style sound wall from the new driveway entrance at the westernmost point of the
property to Foxcroft Lake. The wall would be 16 feet high along Old Reedy Creek Road and along Umstead
State Park, and 16 to 24 feet high around the Dunn residence. The originally proposed chain -link security
fence would still be utilized along I-40 to Crabtree Creek and from Foxcroft Lake east to Crabtree Creek for
security in order to minimize disturbance in these areas. Updated Figure 14 (below) shows the modeled
sound isopleth contours of this newly proposed mitigation.
2/4

Updated 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).
3/4

Table 1 is a summary of the modeled sound levels predicted at the four discrete receptors shown above.
Receptors R-A and R-B were included in the model to evaluate future noise conditions in more detail affecting
the Foxcroft Lake area, and receptors R-C and R-D were added to better evaluate the front and back yards
belonging to the Dunn residence. It should be noted these subsequent noise mitigation efforts were voluntary
on Wake Stone's part, and we still maintain they were not statutorily required.
The point of this summary table is to demonstrate that Wake Stone's current proposed design involving a
slightly larger Pit 2 with concrete panel wall in place of the earthen berm perform as well or better to reduce
noise levels affecting Umstead Park and the Dunn residence. Thus, it can be shown (in Table 1) that Wake
Stone's current proposed design is as good or better at reducing noise as the design proposed in the report
dated 3/12/21 at the majority of receptors.
Table 1. Summary of Wake Stone Quarry Predicted Sound Levels
Noise Receptor
Predicted Noise Levels from Wake Stone Operations
For Worst -Case 280 feet Production Scenario (Leq(h) dBA)
Final Report
3/12/21
Current
Proposal
Change in
Noise Level
Comments
R-1: Residence Property Line
48.6
43.1
- 5.5
Notably quieter
R-2: Company Mill Trail
52.4
52.4
0.0
R-3: Picnic Area
52.1
52.1
0.0
R-4: Residences
35.2
35.2
0.0
R-5: Reedy Creek Park Trail
38.6
38.5
-0.1
Slightly quieter
R-6: North Turkey Creek Trail
31.1
31.1
0.0
R-7: Foxcroft Lake
53.2
53.0
-0.2
Slightly quieter
R-8: Crabtree Creek
50.3
51.0
0.7
Slightly louder
R-A: Near Foxcroft Lake
55.4
55.4
0.0
R-B: Foxcroft Property Line
57.1
56.7
-0.4
Slightly quieter
R-C: Dunn Back Yard
53.3
51.7
-1.6
Slightly quieter
R-D: Dunn Front Yard
45.0
44.1
-0.9
Slightly quieter
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).
ea, -t4J1V___
ERICH THALHEIMER
INCE BOARD CERTIFIED NO. 20104
414