Appendix E - Blast Impact Study

Piedmont Lithium Carolinas, Inc. Response to DEMLR Additional Information Request
Appendices
PIEDtA'ONT
LITHIUM
E
Appendix
Study
E: Blast Impact

• *> AUSTIN POWDER
December 6t", 2021
To:
Patric❑ Brindle
32 North Main St., Suite 100
Belmont, NC 28012
Luke Provencher, Director of Technical Services
Austin Powder Company — North America
Piedmont Lithium Blasting Impact Study
Austin Powder was as—ed to conduct a blasting impact study for the proposed Piedmont Lithium operation in
Gaston County, North Carolina. This study summarizes a review of the possible impacts from blasting operations
on the surrounding communities and includes considerations for managing ground vibrations, air overpressure, and
flyroc- ris a
Community Impact — Summary
Multiple simulations were run using Austin Powder's proprietary blast modelling software to validate the potential
impacts on the neighboring communities for the proposed Piedmont Lithium operation in Gaston County, North
Carolina. The three primary blasting impacts studied are ground vibrations, air overpressure, and flyroca All three
concerns were simulated based on the assumed blasting parameters coupled with the best information available at
the time of this study. This study has incorporated the blasting -related requirements of the Gaston County Unified
Development Ordinance (UDO).
The South Pit is the planned starting point for blasting operations, so this was used as the primary location for the
blasting simulations. The blasting conditions for the entire mine site are expected to be comparable to the
assumptions used in the South Pit, so the blasting impact simulations from the South Pit can reliably be applied to
blasting in the North Pit, West Pit, and East pit. In accordance with the UDO, all blasting impact simulations
accounted for a minimum proximity of 500' from any occupied dwellings for all pits. Once blasting commences,
site -specific data can be collected on a shot -by -shot basis to create historical data to better predict the effects of
ground vibration, air overpressure, and flyroc❑for future blasts. Figure 1 shows an overview of the proposed
Piedmont Lithium mine site and the closest occupied dwellings to the whole mine site.
The simulations show with a high level of confidence that blasting operations can be carried out safely while
maintaining minimal impacts on the neighboring communities to include ground vibration, air overpressure, and
flyroc—
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Figure 1 — Mine site overview with locations for South Pit blast simulations and all closest occupied dwellings
Assumed blasting parameters
The potential impacts of the blasting operations are dependent on the assumed parameters of the intended blast
design(s). Below is a list of the assumed parameters for the initial blast design.
• Number of holes per shot — 69
• Depth of holes — 43'
• Hole diameter — 5.5"
• Burden & Spacing — 12' x 15'
• Stemming length — 11'
• Explosives per hole — 396 lb
It is important to note that these parameters are subLoct to change once blasting operations begin.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• #> AUSTIN POWDER
Community Impact — Blast Vibration
The ground vibrations generated from blasting will be measured with seismographs which record the peal] particle
velocity (in/s) and vibration frequency (Hz) for a blast. The "Z-Curve" (seen below in Figure 1) was developed by
the former United States Bureau of Mines (USBM) and is the standard for plotting and reviewing the blast vibrations
on neighboring structures in the state of North Carolina. To maintain compliance no maximum ppv of the ground
motion shall not exceed the solid blac❑line in Figure 2 as monitored at the nearest protected structure.
,oa
2 Irwrxec
s�
2
� o.oaa in
G
Q 1.0
w 4,T5 InNec
> d
w
�' 4,SQ Inrsec ��
*&ter �
lz--------
0,090
.1
1 14 100
FREQUENCY,Hz
Figure 2 — Z-Curve as developed by USBM
While it's impossible to predict the exact peak particle velocities (ppv) for a proposed blast it is possible to predict
the liJaly upper limit of the ppv with a high level of confidence based on the assumed blast parameters, the
geologic characteristics of the roCE (in the form of a K factor), and the proximity to the neighboring structure(s).
Frequencies cannot be reliably predicted at this stage so the impact study will focus on identifying IiCjely predicted
ppv based on the intended blast designs. Austin Powder reviewed the previous two-year blast history from an
operation in the Kings Mountain, NC area which features similar geology and blasting configuration to the proposed
Piedmont Lithium's operation. This historical data can be applied as a baseline geologic characteristic model for the
initial ppv predictions for this study.
The initial blasting is expected to take place in Piedmont Lithium's "South Pit" and will be over 1,600' from the
nearest protected structure (NPS). Based on the previously assumed blasting parameters, assumed K factor, and
initial blast proximity the ppv is not expected to exceed 0.16 in/s. These ppv levels are not expected to have
adverse effects on the integrity of the neighboring structures. Figure 3 below shows the predicted vibration contour
model for the initial blast in the South Pit.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Figure 3 — Blast vibration contours for initial blast in South Pit
Blasting will progress to the west toward the NPS but will not exceed a minimum proximity of 500' in accordance
with the UDO. Based on the same blast parameter assumptions, K factor, and a 500' blast proximity the predicted
ppv is not expected to exceed 0.8 in/s. As blasting gets closer to the NPS the resulting frequencies are IiEely to
increase which will help minimize the effects of any potentially higher ppv levels. These ppv levels are not
expected to have adverse effects on the integrity of the neighboring structures. Figure 4 below shows the predicted
vibration contour model for the closer proximity blasts in the South Pit.
Figure 4 — Blast vibration contours for closest blast in South Pit
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Once blasting operations commence, the recorded ground vibration for each blast can be used as a data point to
establish a site -specific K factor which can be used to better predict ppv and in some cases frequencies for
subsequent blasts. Alternative blast design strategies, explosive product types, and blast timing plans can be
implemented if ground vibration levels need to be reduced to maintain compliance with the monitoring requirements.
The results of the ground vibration modelling simulations provide a high level of confidence that blasting operations
can be safely executed based on the assumed blast parameters while maintaining compliance and minimizing
negative effects on neighboring properties.
Community Impact — Air Overpressure
Air overpressure is the energy that escapes from a blast into the atmosphere in the form of sound waves and is
measured in decibels (dB). The same seismographs that will be used to measure the ground vibration will also be
measuring the air overpressure on each blast using a dedicated microphone. The state of North Carolina requires
air overpressure readings fall below 133 dB when using a 2.0 Hz microphone which is the assumed microphone
setup for this study. Using the same assumed blast parameters, and an understanding of the orientation and
proximity of the blasts we can similarly prolect the IiCely overpressure readings at neighboring structures. Figure 5
below shows the air overpressure contours for the initial blast in the South Pit.
Figure 5 — Air overpressure contours for initial blast in South Pit
Figure 5 shows that the initial blasting of approximately 1,600' away is IiCely to produce overpressure levels well
below the maximum allowable limit of 133 dB.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Blasting will progress to the west toward the NPS but will not exceed a minimum proximity of 500' in accordance
with the UDO. Based on the same assumed blast parameters and the adjusted blast proximity of 500' an additional
overpressure contour model can be generated as shown below in Figure 6.
Figure 6 — Air Overpressure contours for closest blast in South Pit
Figure 6 shows that even as the blasting approaches the minimum distance of 500' from the NPS the simulation
suggests the blasting is liJaly to continue to produce overpressure levels well below the maximum allowable limit of
133 dB.
Once blasting operations commence, the recorded air overpressure for each blast can be used as a data point to
establish a site -specific history of air overpressure performance based on pertinent blast parameters. Alternative
techniques can be applied (if required) to further minimize the resulting overpressure Via reorientation of the blast,
adasting the amounts and types of stemming material, altering the blast design parameters, and applying unique
timing solutions.
The results of these air overpressure modelling simulations provide a high level of confidence that blasting operations
can be safely executed based on the assumed blast parameters while maintaining compliance and minimizing
negative effects on neighboring properties.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Community Impact - Flyrock
One of the primary safety concerns due to blasting is the potential for flying roc❑or material. Fyyroc❑can be
generated either from the top, or collar, of the blast or from the front, or free face, of the blast. It is of paramount
importance that all shots are designed to have adequate confinement in the form of adequate stemming and
adequate face burdens to help minimize the potential riSEfor flyroc❑with each design. Austin Powder can use the
assumed design parameters and approximate orientation of proposed blasts to quantify the potential flyroc❑ris-for
each blast design.
Figure 7 below shows a worst -case flyroc❑ris❑assessment based on the assumed blasting parameters and the
shot orientation and proximity of the initial blasting in the South Pit. The red ring represents the maximum potential
flyroc- ris❑based on the assumed collar and face design parameters, and the yellow ring represents an arbitrary
but definable safety factor which can represent a minimum require personnel clearance zone. A safety factor of 1.5
times the maximum flyroc❑ris-was assumed for these simulations.
Figure 7 - Flyrock risk assessment map for initial blast in South Pit
The initial blasting in the South Pit is not expected to generate an unsafe flyroc-ris❑for the neighboring communities
based on the assumed design parameters and proximity to the blast.
Blasting will progress to the west toward the NPS but will not exceed a minimum proximity of 500' in accordance
with the UDO. Based on the same assumed blast parameters and the ad-usted blast proximity of approximately
500' an additional flyrock risk map has been generated and can been seen below Figure 8.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Figure 8 — Flyrock risk assessment map for 500' proximity blast in South Pit
When blasting 500' from the neighboring structures the simulation shows some structures now fall within the assumed
1.5 safety factor clearance zone. This highlights an increased ris❑and may require adastments to the blast design
to further minimize the risa Figure 9 below shows the resulting flyroc❑ris❑simulation assuming an ad�dstment to a
4.5" borehole diameter, with 11' of stemming, and approximately 265 lb of explosives per hole. These adjustments
may not represent actual blast design parameters but are meant to show the potential impacts on the flyrocD risa i
assessment for a potential blast design.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com

• *> AUSTIN POWDER
Figure 9 — Adjusted flyrock risk assessment map for 500' proximity blast in South Pit
The applied pattern adastments show an improvement in the overall flyroc❑ris❑assessment as shown in Figure 9
which confirms realistic pattern adastments can be introduced to manage and reduce potential flyrocEris❑as
needed based on shot orientation and proximity to neighbors. Once blasting operations commence each blast can
be reviewed to confirm actual roc❑movement post -blast. This data can be used to create a historical reference for
typical roc❑ movement based on blast parameters in different areas of the pit to help improve the site -specific
accuracy of the ris❑assessment model.
These simulations show that the assumed blasting parameters can be applied safely based on the proposed
orientation and proximity of blasting in the South Pit.
AUSTIN POWDER COMPANY
25800 Science Park Dr. MOBILE: [phone] [e-mail]
Cleveland. OH 44122 wvvw.austinDowder.com