Appendix G.0

Piedmont Lithium Carolinas, Inc. Response to DEMLR Additional Information Request
Appendices
a
PIEDMONT
LITHIUM
G
Appendix G: Response to
DEMLR Mooresville Regional
Office Comments

Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
Comments on Carolina Lithium Project by MRO Staff
Gaston County 36-35
List of Attachments Referenced Herein:
Attachment 1 Overall Mine Map and Reclamation Map (Sheets 1-2)
Attachment 2 Concentrate Operation Drawings (Sheets 1-34)
Attachment 3 Supporting Concentrate Operations Documentation
3.1 Piedmont Carolina Lithium Mine #1 Pit Sequencing Specifications (Sheets 1-4)
3.2 Road and Conveyor Construction Specifications
3.3 Ditch General Construction Specifications
3.4 Sediment Structures - General Constructions Specifications
3.5 Guideline Technical Specification for the Waste Roc
3.6 Concentrate Operations Drainage Calculations
3.7 Waste Rock and Topsoil Pile Stability Analysis
Attachment 4 Lithium Hydroxide Conversion Plant Drawings (Sheets 1-20)
Attachment 5 Supporting Conversion Operations Documentation
5.1 Road, Parking, Walls, Fencing, and Stream Crossing Construction
Specifications
5.2 Rail Construction Specifications
5.3 Drainage and Sediment Structure Specifications
5.4 Conversion Plant Drainage Calculations
1. The scale I" = 200 feet on the plans are very difficult to see existing and proposed
overland flows. Overview sheets are needed to see the entire project; however,
smaller scale plans areneeded to properly show overland flows. Provide sheets as
necessary.
1 "=100' scale maps for the proposed project have been created for the Site / Mine Map,
Reclamation Map, and Drainage Analysis Map to clarify the detailed designs for the project. The
overall and small-scale maps can be found in Appendix G, Attachments 1 and 2.
For the Conversion Plant site, 1 "=200' scale maps show the overall site, and 1 "=50' scale maps
are provided to show the sediment basin designs (Appendix G, Attachment 4).
2. The overview sheets are showing areas to be developed; however, smaller scale
plans havenot been provided for these locations (e.g. concentrate plant, solar farm,
etc.).
1 "=100' scale maps for the proposed project have been created for the Site / Mine Map,
Reclamation Map, and Drainage Analysis Map to clarify the detailed designs for the project. The
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
overall and small-scale maps can be found in Appendix G, Attachments 1 and 2. A note has been
placed on the Site / Mine Map to show the Solar Farm as future development.
3. Ensure plans show existing and proposed topo contours on all sheets. In addition,
ensurecontours are labeled on all sheets.
All sheets clearly show existing and proposed topographic contours with labels.
4. All streams and water bodies need to be clearly shown on the plans. Adequate
undisturbed stream buffers must be provided. Provide a legend to denote stream
buffer on plans. All land disturbance and proposed measures must be relocated
out of the required stream buffers. All 401/404 impact areas and non -impact areas
needs to be clearly indented on the plans.
Streams and water bodies are shown on the plans. Jurisdictional waters approved to be disturbed
under the 401/404 are now labeled on the applicable design sheets located in Appendix G,
Attachment 2. Stream buffers are shown on all applicable design sheets located in Appendix G,
Attachments 1 and 2. Also, non -impact areas are now labeled on the Site / Mine Map located in
Appendix G, Attachment 1.
5. Basins must be designed for the maximum drainage area throughout all phases of
construction. Provide drainage area delineation maps for pre & post construction
for sizing ofbasins. Emergency spillways need to be located on natural ground. The
principle spillway systems need to be located away from emergency spillways.
Basins throughout entire projectneed to have a specific ID number. Basins need to
have skimmers for dewatering and plans need to show skimmers in basins &
construction details. Cross-section details for basins need to show the minimum
required crest width. Ensure skimmer basins have baffles. Basins should be
located within the existing natural drainage channels and/or below proposed fill
slopes. Basins should not be located on fill slopes. It is unclear why some basins
have two barrel pipes being shown. It is recommended that one large sized pipe be
provided for the barrel pipes instead of the double -barrel pipes.
The Erosion and Sediment Control (ESC) structures have been designed for the maximum
disturbance for each drainage area. Please see the Drainage Analysis Map (Sheet 8 of 34) in
Appendix G, Attachment 2 for the delineated drainage areas for each structure. The ESC design
for the Concentrate Operations will control all stormwater runoff for the disturbed areas of the
Concentrate Operations site. The Sediment Basins, Sediment Traps, Ditches, and Culverts are
designed on a 25-year, 24-hour storm event.
The Pit Dewatering Ponds have been over -designed to provide storage for the combination of the
maximum expected pit dewatering activities (-2,300 gallons per minute) and a 100-year, 24-hour
storm event. The Pit Dewatering Ponds are designed to store approximately 1,000,000 gallons of
water from the pit area as needed during operations. The Pit Dewatering Pond spillways are
designed to discharge 100 cubic feet per second, which exceeds the combination of the 100-year,
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
24-hour storm event flow of 44.01 cubic feet per second and 2,300 gallons per minute (6.15 cubic
feet per second) pumped flow. The Pit Dewatering Ponds are designed with a level bottom and an
earthen dam with rock spillway to capture and retain flow, allowing time for sediment to settle and
water to discharge only from the top of the structure at the spillway location. The earthen dam
portion of the Pit Dewatering Ponds are designed to function much like a skimmer in that the
volume of water is held internal to the dam and discharged from the top elevation of the dam to
allow for maximum settlement time. The detail sheet for the Pit Dewatering Ponds associated with
the Concentrate Operation is located within Attachment 2, Appendix G on Sheet 34 of 34.
ESC structures will be cleaned out at 50% capacity and are designed with 1 foot of freeboard per
regulations. The Sediment Basins and Sediment Traps have been designed to meet a required
surface area of 435 square feet per calculated cubic feet per second of Q25 peak flow, as well as
storage volume of 3600 cubic feet per disturbed acre which doubles the capacity for sediment
storage for each Sediment Basin and Sediment Trap. This over design in sediment capacity will
assist in the event of a 25-year storm with expanded storage area within the structure to slow and
retain flow to create an adequate flow path/settling time through the structure.
Sediment Basins are designed with a level bottom and a non -perforated riser. All risers are 72-inch
square concrete risers with heights ranging from 4 feet for Sediment Basin SB-17 which has a
required volume of 18,036 cubic feet at 3600 cubic feet per disturbed acre and a provided volume
of 35,129 cubic feet; to a heigh of 8.27 for Sediment Basin SB-11 which has a required volume of
13,500 cubic feet at 3600 cubic feet per disturbed acre and a provided volume of 52,881 cubic feet.
Principle Spillways are now located away from proposed emergency spillways. Emergency
spillways proposed for the sediment basins are grouted rip rap structures. Sediment Basin Details
are located in Appendix G, Attachment 2 on Sheets 9 through 25 of 34.
A summary of the associated drainage area, design storm, calculated Q25 flow, required surface
area, required volume, provided surface area, and provided volume for each ESC structure is
included on the Drainage Analysis Map (Sheet 8 of 34) in Appendix G, Attachment 2. Insets of the
Drainage Analysis Map have also been provided in Appendix G, Attachment 2 (Sheets 8A through
8J). Additional details can be found in Appendix G, Attachment 3.6 and on the Detail Sheets
located in Appendix G, Attachment 2 on Sheets 32 through 34 of 34. The drainage structures
designed for the Concentrate Operations site will be constructed prior to disturbance within the
applicable drainage area and have been designed on maximum flow and disturbance for activities
within the applicable drainage area.
For the Conversion Plant, phasing was adjusted as requested. Phase 1 is pre -construction
conditions and staging areas, and Phase 2 is post-construction/fully developed. Drainage area
maps are provided for both pre- and post -construction. The ESC design will collect all stormwater
runoff for the maximum disturbed area. The Sediment Basins, Sediment Traps, and Culverts are
designed on a 25-year, 24-hour storm event. ESC structures were designed as described above
for the concentrate operations.
Spillway locations have been adjusted to be as close to natural grade as possible, and to be
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
located away from the principal spillway. Skimmers and baffles are included in the sediment basin
design for the Conversion Plant site. The sediment basins for this site are relatively shallow,
resulting in a shorter riser, and requiring the use of double -barrel pipes instead of one larger barrel.
These double barrels are accounted for in the design calculations.
Conversion Plant Drainage Analysis Maps are included in Appendix G, Attachment 4, and
calculations are in Appendix G, Attachment 5.4.
6. It is recommended that the project follow the NCG01 design guidelines. The
drainage area of proposed sediment traps has to be less than 1.0 acre. Skimmer
basins are required for drainage areas of 1.0 acre or more. All proposed sediment
traps need to have a specific ID number.
Sediment Traps are associated with the designed haul roads, access roads, screening berms, and
the magazine location. The Sediment Traps are designed with a level bottom and an earthen dam
with rock spillway to capture a 25-yr, 24-hour storm event and retain flow, allowing time for
sediment to settle and water to discharge only from the top of the structure at the spillway location.
The earthen dam portion of the Sediment Traps are designed to function much like a skimmer in
that the volume of water is held internal to the dam and discharged from the top elevation of the
dam to allow for maximum settlement time. Each Sediment Trap is designed to meet a required
surface area of 435 square feet per calculated cubic feet per second of Q25 peak flow, as well as
storage volume of 3600 cubic feet per disturbed acre which doubles the capacity for sediment
storage. While drainage areas for the Sediment Traps range from 0.29 disturbed acres (Sediment
Trap ST-28 which has a required volume of 1,044 cubic feet at 3600 cubic feet per disturbed acre
and a provided volume of 10,245 cubic feet) to 9.09 disturbed acres (Sediment Trap ST-1 which
has a required volume of 13,482 cubic feet at 3600 cubic feet per disturbed acre and a provided
volume of 43,661 cubic feet), the elevated spillway and overdesign of storage volume provides
retention time within the designed structures. The detail sheets for each Sediment Trap associated
with the Concentrate Operation are located within Appendix G, Attachment 3.6.
7. Provide design calculations for all proposed sediment traps and basins. Ensure
stage storage data is provided. In addition, ensure the required surface area is
provided at proper elevations.
Design calculations are provided in the Appendix G, Attachment 3.6 for all Sediment Basins,
Sediment Traps, Culverts, etc. A Summary of the associated drainage area, design storm,
calculated Q25 flow, required surface area, required volume, provided surface area, and provided
volume for each ESC structure is included on the Drainage Analysis Map (Sheet 8 of 34) in
Appendix G, Attachment 2. Insets of the Drainage Analysis Map have also been provided in
Appendix G, Attachment 2 (Sheets 8A through 8J). The summary table also includes the provided
surface area and storage volume at the proper elevations for each structure. Additional details can
be found in Appendix G, Attachment 3.6 and on the Detail Sheets located in Appendix G,
Attachment 2 on Sheets 32 through 34 of 34.
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
For the Conversion Plant, Drainage Analysis Maps are included in Appendix G, Attachment 4, and
calculations are in Appendix G, Attachment 5.4.
8. Adequate diversion berms need to divert all overland flow into basins. Ensure
diversion berms have positive drainage and enter upper reaches of basin. Provide
adequately sizedslope drains to convey run-off into basins.
Surface disturbance proposed for the Concentrate Operation will be controlled through diversions
and retention structures as shown on the Drainage Analysis Map (Sheet 8 of 34) in Appendix G,
Attachment 2. Insets of the Drainage Analysis Map have also been provided in Appendix G,
Attachment 2 (Sheets 8A through 8J). Additional details can be found in Appendix G, Attachment
3.6 and on the Detail Sheets located in Appendix G, Attachment 2 on Sheets 32 through 34 of 34.
9. The intent and purpose of the proposed "Flumes" into basins are unclear. It appears
some flumes and ditches have ninety -degree bends to divert water into basins. It is
unclear how these can properly function during field conditions. Make sure flow from
the flumes can be handled adequately by the proposed diversion ditches directing flow
towards basins. Clarifyintent as necessary.
Flumes carrying stormwater drainage into the applicable sediment basin or outlet protection into
the basin will be constructed to ensure a non -erodible path for the stormwater is provided for
entrance to the ESC structure. The flow paths have been designed to function during field
conditions. Please see Appendix G, Attachment 3.5 for the typical flume detail as a supplement to
this response.
10.The proposed Sediment Basin #9 (Sheet 17 of 34) does not appear that it will function
as intended. Suggest expanding basin width as necessary to allow basin to properly
function.
Sediment Basin No. 9 has been revised to better store sediment volume throughout the structure
per agency guidance.
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
11.Adequate measures have not been provided below all proposed disturbed areas and/or
throughout all phases of construction. Adequate perimeter measures must be
provided. Diversion berms need to be provided along the outer perimeter of site to
adequately sized skimmer basins. Phase 1 erosion control plans need to show existing
conditions with adequate proposed measures below all disturbed areas. Phase 2 plans
need to show proposed site development improvements, including proposed topo
contours, with adequate measures located below all disturbed areas. It may be
necessary to provide more phasing on such a large site. All proposed utilities to
buildings must be shown on the plans. All proposed storm drainage systems need to
be shown and identified on the plans.
Temporary Diversion Ditches will be constructed around the proposed pits prior to disturbance of
the pit areas. These diversions will intercept surface flow to prevent it from leaving the area. The
temporary ditches will remain until the pit area size is adequate to hold water to be pumped to the
designed Pit Dewatering Ponds. Surface flow from the temporary ditches will be directed to Pit
Dewatering Ponds until the pit area size is adequate to hold water. Detail for Temporary Ditches
are located within Appendix G, Attachment 2 on Sheet 34 of 34. Please see the Drainage Analysis
Map (Sheet 8 of 34) and insets location in Appendix G, Attachment 2 for flow diversion details.
Additional details have been included for the construction of Stream Crossing No. 1, Stream
Crossing, No. 2, and the Whitesides Road Crossing. Please see Appendix G, Attachment 2,
Sheets 29 through 31 B.
For the Conversion Plant, phasing was adjusted as requested. Phase 1 is pre -construction
conditions and staging areas, and Phase 2 is post-construction/fully developed. The ESC design
will collect all stormwater runoff for the maximum disturbed area. Drainage Analysis Maps are
included in Appendix G, Attachment 4, and calculations are in Appendix G, Attachment 5.4.
12.Adequate measures must be provided throughout all phases of the proposed
permanent stream crossings (e.g. pre & post construction). In addition, all stream work
must be conducted "In the Dry." Provide adequate construction sequence and details
as necessary. Typically, adequately sized basins will be needed at all four comers of
the crossing along with diversion ditches. All stream crossings need to be labeled on
the plans to show location. Ensure to provide a specific stream crossing ID number. It
is unclear how proposed arch culvert for Stream Crossing #2 (Sheet 13 of 18) will be
installed. Ensure wall foundation locations are shown on the plans. Will the arch
culvert have a bend without relocating stream channel? Make sure the proposed
stream impacts are covered in your 401/404permits.
Jurisdictional waters approved to be disturbed under the 401/404 are now labeled on the
applicable design sheets located in Appendix G, Attachment 2. Stream buffers are shown on all
applicable design sheets located in Appendix G, Attachment 2. Also, non -impact areas are clearly
labeled on the Site / Mine Map located in Appendix G, Attachment 1. Additional information
pertaining to the construction of Stream Crossing No. 1, Stream Crossing No. 2, and the
Whitesides Road Crossing can be found in Appendix G, Attachment 2 on Sheets 29 through 31 B
of 34.
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
For the Conversion Plant, there are no stream impacts, as noted on the plans Appendix G,
Attachment 4. Allowable buffer impacts are shown in accordance with the most recent Gaston
County UDO.
13. Provide sizes and pipe material for proposed culverts on the plans. Ensure all design
calculations are provided for sizing culverts. Provide legend to identify pipes. Ensure
allproposed storm drainage systems are clearly shown and identified on the plans.
Proposed culvert sizes, pipe materials, design requirements, etc. can be found on the Culvert
Summary Table located within Appendix G, Attachment 3.6. The associated hydrographs are
located following the Culvert Summary Table. The proposed culverts can be found labeled on the
drawings and included in the legends in Appendix G, Attachments 1 and 2.
For the Conversion Plant site, culvert sizes and materials are labeled on the plans. Calculations
can be found in Appendix G, Attachment 5.4.
14. Need to clearly identify all temporary and permanent outfalls. The outfall numbering
systemshould match the industrial storm water permit map.
NPDES outfall numbering systems are now included on the Drainage Analysis Map (Sheet 8 of 34)
and coordinated with the NCG02 application (Appendix G, Attachment 2). All outfalls associated
with the Concentrate Operations are permanent for the life of the mine. Outfalls for the Conversion
Operations include a mixture of temporary outfalls (i.e. erosion and sediment controls) and
permanent outfalls (i.e. controls retained for post construction stormwater management).
Permanent outfalls are accounted for in the NPDES outfall numbering systems.
15.Should they apply for a NCG02 Storm water permit for mining, or should an individual
stormwater permit be required for the chemical plant?
The NCG02 Notice of Intent application has been submitted for this project (Appendix D).
16. Please provide locations for the concrete washout station with measures. These
should notbe located within 50 feet of any storm drain, basin, or stream.
Please see the Site / Mine Map in Appendix G, Attachment 1 for the proposed location of concrete
washout stations, as well as Sheet 32 of 34 in Appendix G, Attachment 2 for the typical
construction details of the concrete washout station for the Concentrate Operation.
Conversion plant plans include concrete washout locations as requested (Appendix G, Attachment
4), as well as construction details (Appendix G, Attachment 5.3).
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
17. Make sure the legend specified all symbols/lines shown on the plan. A legend for
erosion and sedimentation control measures and their corresponding symbols or
line -types has not been provided on the plan or not very clear.
All symbols/lines are now shown on plan sheets and within legends.
18.Please identify measures that have already been installed, and those measures that
are proposed.
Measures have not been installed for the Concentrate Operations site. One existing bridge on
Hephzibah Church Road will be upgraded for heavy equipment usage. This existing bridge is
labeled on the applicable sheets. Proposed measures are located within this package (Appendix
G, Attachments 1-3).
Measures have not been installed for the Conversion Plant site. Proposed measures are located
within this package (Appendix G, Attachments 4-5).
19. Please provide sequentially phased construction and provide very detailed
sequencing such that the extent and duration of the land -disturbing activity is
minimized.
Please see the narratives located in Appendix G, Attachment 3 of this package for descriptions of
construction activities for the Concentrate Operation.
For the Conversion Plant, the phasing was adjusted as requested. Phase 1 is pre -construction
conditions and staging areas, and Phase 2 is post-construction/fully developed. The ESC design
will control all stormwater runoff for the maximum disturbed area. All drainage designs comply with
the Mine Permit Application and NCG02 requirements. Drainage Analysis Maps are included in
Appendix G, Attachment 4, and calculations are in Appendix G, Attachment 5.4.
20. Modification of the baffle configuration is necessary to achieve the desired volume
betweenbaffles, to allow the longest water path for settling and to allow access for
maintenance. Show the baffle placement on the plans indicative of field conditions.
Baffle configuration has been designed to achieve desired volume between baffles, allow
necessary maintenance, and allow for longest water path for entering flow. Please see Appendix
G, Attachment 2 design sheets for baffle locations as well as Appendix G, Attachment 3.6 for
drainage design calculations.
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
21. Please specify the skimmer size, orifice diameter, and barrel diameter on the plans.
Different branded skimmers have different design and operational parameters.
Please specify the skimmer manufacturer on the plans. Please also provide
manufacturer -specific calculations,if not yet provided. Any alternate skimmer must
have calculations submitted and approved prior to installation.
The Pit Dewatering Ponds have been over -designed to provide storage for the combination of the
maximum expected pit dewatering activities (-2,300 gallons per minute) and a 100-year, 24-hour
storm event. The Pit Dewatering Ponds are designed to store approximately 1,000,000 gallons of
water from the pit area as needed during operations. The Pit Dewatering Pond spillways are
designed to discharge 100 cubic feet per second, which exceeds the combination of the 100-year,
24-hour storm event flow of 44.01 cubic feet per second and 2,300 gallons per minute (6.15 cubic
feet per second) pumped flow. The Pit Dewatering Ponds are designed with a level bottom and an
earthen dam with rock spillway to capture and retain flow, allowing time for sediment to settle and
water to discharge only from the top of the structure at the spillway location. The earthen dam
portion of the Pit Dewatering Ponds are designed to function much like a skimmer in that the
volume of water is held internal to the dam and discharged from the top elevation of the dam to
allow for maximum settlement time. The detail sheet for the Pit Dewatering Ponds associated with
the Concentrate Operation is located within Appendix G, Attachment 2 of this package on Sheet 34
of 34.
ESC structures will be cleaned out at 50% capacity and are designed with 1 foot of freeboard per
regulations. The Sediment Basins and Sediment Traps have been designed to meet a required
surface area of 435 square feet per calculated cubic feet per second of Q25 peak flow, as well as
storage volume of 3600 cubic feet per disturbed acre which doubles the capacity for sediment
storage for each Sediment Basin and Sediment Trap. This over design in sediment capacity will
assist in the event of a 25-year storm with expanded storage area within the structure to slow and
retain flow to create an adequate flow path/settling time through the structure.
Sediment Basins are designed with a level bottom and a non -perforated riser. All risers are 72-inch
square concrete risers with heights ranging from 4 feet for Sediment Basin SB-17 which has a
required volume of 18,036 cubic feet at 3600 cubic feet per disturbed acre and a provided volume
of 35,129 cubic feet; to a heigh of 8.27 for Sediment Basin SB-11 which has a required volume of
13,500 cubic feet at 3600 cubic feet per disturbed acre and a provided volume of 52,881 cubic feet.
Sediment Basin Details are located in Appendix G, Attachment 2 on Sheets 9 through 25 of 34.
Sediment Traps are associated with the designed haul roads, access roads, screening berms, and
the magazine location. The Sediment Traps are designed with a level bottom and an earthen dam
with rock spillway to capture a 25-yr, 24-hour storm event and retain flow, allowing time for
sediment to settle and water to discharge only from the top of the structure at the spillway location.
The earthen dam portion of the Sediment Traps are designed to function much like a skimmer in
that the volume of water is held internal to the dam and discharged from the top elevation of the
dam to allow for maximum settlement time. Each Sediment Trap is designed to meet a required
surface area of 435 square feet per calculated cubic feet per second of Q25 peak flow, as well as
storage volume of 3600 cubic feet per disturbed acre which doubles the capacity for sediment
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
storage. While drainage areas for the Sediment Traps range from 0.29 disturbed acres (Sediment
Trap ST-28 which has a required volume of 1,044 cubic feet at 3600 cubic feet per disturbed acre
and a provided volume of 10,245 cubic feet) to 9.09 disturbed acres (Sediment Trap ST-1 which
has a required volume of 13,482 cubic feet at 3600 cubic feet per disturbed acre and a provided
volume of 43,661 cubic feet), the elevated spillway and overdesign of storage volume provides
retention time within the designed structures. The detail sheets for each Sediment Trap associated
with the Concentrate Operation is located within Appendix G, Attachment 3.6 of this package.
Typical Sediment Trap Cross Section:
Normal Pool El. SPILLWAY
50% Cleanout El.
2� 21
BOTTOM OF TRAP
A summary of the associated drainage area, design storm, calculated Q25 flow, required surface
area, required volume, provided surface area, and provided volume for each ESC structure is
included on the Drainage Analysis Map (Sheet 8 of 34) in Appendix G, Attachment 2 of this
package. Insets of the Drainage Analysis Map have also been provided in Appendix G, Attachment
2 (Sheets 8A through 8J). Additional details can be found on the Detail Sheets located in Appendix
G, Attachment 2 of this package on Sheets 32 through 34 of 34. The drainage structures designed
for the Concentrate Operations site will be constructed prior to disturbance within the applicable
drainage area and have been designed on maximum flow and disturbance for activities within the
applicable drainage area.
Skimmer calculations for the Conversion Plant are provided in Appendix G, Attachment 5.4, with
detailed skimmer requirements shown on plan sheets in Appendix G, Attachment 4. Any skimmer
provided by the contractor for construction must be verified by the engineer to meet the
requirements of these plans.
22. Permanent/Temporary slope drains should be provided where temporary diversions
discharge into sediment basins or traps with a slope height greater than seven feet.
Diversions should be installed to the slope drains to prevent sheet flow over
sediment basin slopes greater than 7 feet.
Temporary Diversion Ditches will be constructed around the proposed pits prior to disturbance of
the pit areas. These diversions will intercept surface flow to prevent it from leaving the area. The
temporary ditches will remain until the pit area size is adequate to hold water to be pumped to the
designed Pit Dewatering Ponds. Surface flow from the temporary ditches will be directed to Pit
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
Dewatering Ponds until the pit area size is adequate to hold water. Details for Temporary Ditches
are located within Appendix G, Attachment 2 of this package on Sheet 34 of 34.
23.When operating a pump around system the water shall be flow in the work area
must be pumped around the work area and discharged in a stable manner
downstream of the work area. Pump must be an adequate size to accomplish the
pump around.
Please see Appendix G, Attachment 3.2 for operation details for a pump around system for the
Concentrate Operation.
24.Silt fencing below fill slopes should be installed a minimum of 10 feet off the
proposed toe of the slope. This will allow room for sediment storage and
maintenance access, as well as minimize the potential for damage to the silt fence
during fill slope construction.
Silt fence will be installed a minimum of 10 feet off of the proposed toe of slope. A note has been
added to the Site / Mine Map to state this requirement.
25.A construction entrance should be provided on the plans where construction traffic
will access a paved surface. For the construction entrance, provide turning radius
sufficient to accommodate large trucks. A minimum length of 100' must be provided
for the construction entrance/exit.
Temporary construction entrances have been identified on the Site / Mine Map at five (5) locations
(plant pad, north and south closures of Hephzibah Church Road, Emulsion entrance, and the
Screening (Sound) Wall south of the Waste Rock Pile to be accessed from Charlie Carpenters
Trail) with detail provided on Sheet 32 of 34 for the Concentrate Operations (Appendix G,
Attachments 1 and 2). Screening (Sound) Walls will be constructed with an access road to remain
during and after wall construction.
Typical Screening (Sound) Wall Plan View:
I, --.T TCii `,C AL_I
SCREENING WALL SEDIMENT DITCH
ACGESS ROAD
SC EENING (SOUND) WALL
ACCESS ROAD
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Piedmont Lithium Carolinas, Inc. I I Response to DEMLR Additional Information Request
Appendix G Response to DEMLR Mooresville Regional Office Comments
Temporary construction entrances for the Conversion Plant are shown in Appendix G, Attachment
4 (Sheets 1 and 2 of 20, detail on Sheet 16).
26. Rip rap aprons should not be placed on the fill material. It should be extended far
enough to reach a stable section of the channel. Ensure that the apron has zero
grade
A review of design has been conducted to ensure no rip rap aprons are located on fill material.
27. Provide E&SC measures for the solar farm or label as future development, no land
disturbance for this phase.
A note has been added to the applicable plan sheets that the Solar Farm is to be developed in the
future.
28.Significant plans revisions will be necessary before this plan can be recommended for
permit issuance.
Plans have been revised as stated in the above comment responses.
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