NCG021045_Response to ADI_20250613

4250 Congress Street
Suite 900
Charlotte, North Carolina 28209
980-299-5700 A\\ Albemarle
April 28, 2025
Mr. Corey Clayton, Assistant State Mining Engineer
Division of Energy, Mineral and Land Resources
North Carolina Department of Environmental Quality
Attn: Mining Program
1612 Mail Service Center
Raleigh, North Carolina 27699
RE: Kings Mountain Mine
Archdale Tailings Storage Facility
Response to Request for Additional Information
Dear Mr. Clayton,
Albemarle, Inc. would like to thank you for your comments in response to our North Carolina
Mine Permit Application, submitted on August 2, 2024 for the proposed Kings Mountain Mining
Project (Project).
Please see the following responses to your Additional Information Request, dated October 3,
2024. The agency comments are in bold text and Albemarle's responses are provided in regular
text.
Should you have any questions or require additional information following your review of the
enclosed materials, please contact me at [phone] or at [e-mail].
Sincerely,
John Kuhn
Mine Environmental Permitting Lead
cc: Jerry Eplin, PE, State Mining Engineer
Attachment A NCDEQ Letter Requesting Additional Information
Attachment B Albemarle Response to Request for Additional Information
Attachment C Technical Memorandum: Addendum-01 to Archdale Storm Water
Management Report for Erosion Control Enhancements, Kings Mountain
Mining Project
Attachment D Archdale TSF Reclamation Plan Map
https://www.albemarle.com

ATTACHMENT A
NCDEQ Letter Requesting Additional Information

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ROY COOPER
Governor
MARY PENNY KELLY
Secretary �AM° *
WILLIAM E. TOBY VINSON,JR. NORTH CAROLINA
Interim Director Environmental Quality
October 3, 2024
Certified Mail
Return Receipt Requested
7022 0410 0003 1066 6198
John Kuhn
Albemarle U.S., Inc.
348 Holiday Inn Drive
Kings Mountain,NC 28086
RE: Archdale Tailings Storage Facility
Cleveland County
Broad River Basin
Dear Mr. Kuhn:
We have reviewed the application your company submitted for the referenced mine site. In order for this office to
complete its review of the referenced project in accordance with N.C.G.S. §74-50 and§74-51 of the Mining Act of
1971,please provide the additional or revised information in accordance with the following comments:
1. Please provide the following documents in order for DWR to continue their review to determine
whether the site will have unduly adverse effects on potable groundwater supplies, wildlife, or fresh
water, estuarine, or marine fisheries:
a. Pumping O&M Plan
b. LEAF Study
c. Groundwater/Surface water Monitoring Reports that further describe exceedances of
applicable standards
2. Please address the comments from the Mooresville Regional Office included with this letter.
Please note, this office may request additional information, not included in this letter, as the mining application
review progresses. Be advised that our review cannot be completed until all of the items listed above have been
fully addressed.
D EQl
r—A- North Carolina Department of Environmental Quality I Division of Energy,Mineral and Land Resources
512 North Salisbury Street 1 1612 Mail Service Center I Raleigh,North Carolina 27699-1612
NORhI CAROLINA
oanenmem of Envimomenmi Quality /� 919.707.9200

Certified Mail
7022 0410 0003 1066 6198
Page 2
In order to complete the processing of your application,please forward two(2)copies of the requested information
to my attention at the following address:
Division of Energy,Mineral and Land Resources
Department of Environmental Quality
1612 Mail Service Center
Raleigh,NC 27699-1612
If hand delivering or delivering by shipping company(e.g.,FedEx,UPS),please deliver to our physical address:
Division of Energy,Mineral, and Land Resources
Department of Environmental Quality
512 N. Salisbury Street, 5th Floor
Raleigh,NC 27604
As required by 15A NCAC 513.0113,you are hereby advised that you have 180 days from the date of your receipt
of this letter to submit all of the requested information. If you are unable to meet this deadline and wish to request
additional time,you must submit information,in writing,to the Director clearly indicating why the deadline cannot
be met and request that an extension of time be granted. If an extension of time is not granted, a decision will be
made to grant or deny the mining permit based upon the information currently in the Department's files at the end
of the 180-day period.
Though the preceding statement cites the maximum time limit for your response,we encourage you to provide the
additional information requested by this letter as soon as possible. Your prompt response will help us to complete
processing your application sooner.
Please contact me at(919)707-9228 if you have any questions.
Sincerely,
Co Cl iz.
Corey Clayton
Assistant State Mining Engineer
Enclosures: MRO Comments
cc: Jerry Eplin,PE

ATTACHMENT B
Albemarle Responses to Request for Additional Information

Responses to Request for Additional Information
1. Please provide the following documents in order for DWR to continue their
review to determine whether the site will have unduly adverse effects on
potable groundwater supplies, wildlife, or fresh water, estuarine, or
marine fisheries:
• Pumping O&M Plan
• LEAF Study
• Groundwater/Surface water Monitoring Reports that further describe
exceedances of applicable standards
Pumping and O&M Plan
Albemarle stated, in the permit application, that a pumping and O&M plan not
required because there are no jurisdictional wetlands within or near the project
boundary, and therefore there is no "potential to drain wetlands or other surface
waters" as given in Section G-2 of the NCG02 permit (excerpt given below).
(a)These requirements apply to all mine dewatering, and includes dewatering
from pits for quarries, clay brick, sand and gravel, borrow pits, and refractory
mining, as well as mines with similar discharges.
(b)(b) Permittees conducting mine dewatering activities that have the potential
to drain wetlands or other surface waters shall implement a Pumping
Operation and Monitoring (POM) Plan approved by the Division. The POM
shall be submitted with the NOI for the Division's review and approval.
Written Division approval of the POM is required prior to the discharge of
mine dewatering. (c) POM Plans shall include, but are not limited to: i.
Groundwater monitoring strategies to demonstrate the effect of pumping, ii.
Detailed plans to maintain the surrounding hydrology that protects the
affected streams and wetlands, iii. Monitoring to demonstrate compliance,
and iv. The pumping regime deemed necessary to protect affected streams
and wetlands.
Furthermore, predictive studies have shown that the proposed TSF will have a
minimal effect on groundwater levels and withdrawal rates - Joey will need a little
help here with groundwater flow rates and hydrogeology to bolster the conversation
below
The proposed TSF location is on a pit resulting from prior mining operations, which
is actively dewatered by the current permit holder (IMERYS) under NCG020089.
The ongoing dewatering, which is accomplished by periodic pumping of ponds
formed at the bottom of the pit, consists of both stormwater and groundwater that
infiltration to the pit.
In the future state, the abandoned pit will be filled in with tailings, and stormwater
collected on the tailings surface, will be pumped to the Contact Water Pond.
Similarly, infiltration through the TSF material, and groundwater entering the TSF

material will collected in an underdrain system with a sump, from which it will be
pumped to the Contact Water Pond for discharge. Groundwater infiltration into the
TSF (and rates of removal) will not change substantially from the present case.
Predictive studies show that construction and operation of the proposed TSF will not
cause drawdown outside the property boundary that could impact groundwater
users in the areas around the Archdale site. This information can be found in detail
in the Archdale site water balance report, Technical Report 2023 Prefeasibility Study
Surface Water: Water Balance Development Report Archdale TSF Kings Mountain
Mining Project and in the Hydrogeological Assessment Study for Archdale Tailings
Facility Kings Mountain Mining Project Prefeasibility Study, Figure 6.11
LEAF Study
Relative and pertinent LEAF data for the Archdale site is the LEAF testing done on
future tailings because that is the material that will be in contact with groundwater.
LEAF studies were conducted as part of a comprehensive geochemical study
conducted for the Kings Mountain mine site. Methodology and results are contained
in the Technical Report - 2023 Prefeasibility Study - Baseline Geochemical
Characterization - Kings Mountain Mining Project, which was provided as Appendix
H of the Kings Mountain Mine permit application. An additional copy of this report
has been submitted as an electronic version of this response.
The study addressed the tailings to be stored at the Archdale TSF, the legacy
tailings currently stored at the Kings Mountain site, and the waste rock that will be
transported to the Archdale site to construct the embankment wall.
Specific sections of the report relevant to LEAF testing include
• Executive Summary
• Section 3.2 Sample Collection - Future Tailings
• Table 4-2 Tailings Sampling and Testing Methods
• Section 4.1.2 Laboratory Methods - Future tailings
• 4.4.3 Laboratory Methods - LEAF Testing
• Section 5.2.5 Results and Discussion - Future Tailings Material - Short Term
Leach Tests
Groundwater/Surface Water Monitoring Reports
Albemarle has been conducting routine quarterly surface water and groundwater
sampling from at the Archdale site since fall of 2023. The results of 4 quarterly
monitoring periods (4Q 2023, 1Q 2024, 2Q 2024, and 3Q 2024) are summarized in
the following discussion; the summary reports (with some appendices abridged for
brevity) are provided in the jump drive included with this submittal.

Sampling was conducted at 10 groundwater monitoring wells, and 6 surface water
locations on the project site. Additionally, samples were taken at 4 surface water
locations in the stream network downstream of the project site.
Results were compared to the following standards:
• The North Carolina groundwater standards for Class GA waters (North
Carolina Administrative Code [NCAC] 15A 02L .0202).
• The North Carolina surface water standards for Class C Waters (NCAC 15A
02B .0211).
Results indicate that for the most part, the baseline water quality meets NCDEQ
Class C surface water quality, and NC 2L groundwater standards, with the
exceptions discussed in the reports and tabulated below. Based on geochemical
studies, these exceedances are considered determined to be geogenic in origin
(naturally occurring), therefore not an impact of the prior mining operation.
Additionally, forward looking predictions of water quality for the operational project
do not indicate exceedances of surface water standards at permitted stormwater
discharge points.
Summary of Archdale WQ Sampling Results
#locations #Results Exceeding NC
Period sampled #Results Exceeding NC 2L GA Groundwater Standards 2B Class C Surface
Water Standards
GW SW Co Cr i Be pH pH Fe Pb Mn i V a Cu Pb € Hg Cr
Q3 2023 9 4 8 6 s 1 9 1 1 i
Q12024 9 22 8 1 1 € 4 € 1 9 i 1 1 1
C!2 2024 10 23 9 I - € 6 i 6 ` 3 1 ' 9 - i 1 2 - I 1 1
Q3 2024 10 € 9 9 € - - - 7 1 9 - 1 2 € -
Toto! 38 58 34 1 1 6 6 20 4 36 1 4 5 1 1 1
Notes: All constituents analyzed met standards unless noted here
GW:Groundwater
SW:Surface Water

The following section presents the comments received by the Mooresville Regional Office,
with the additional requested information presented.
1. The Erosion and Sedimentation Control (E&SC) drawings are provided on
11 x 17 sheets and at a scale that is not reviewable on this size sheets.
Provide all E&SC sheets on at least 24 x 36 sized sheets and at a scale that
shows sufficient detail to be reviewable. Clearly show existing versus
proposed contours. As drawn, the E&SC scheme for the site is not clear.
The Plan should clearly show how erosion and sedimentation will be
controlled during each phase of the project.
Responses to this question, as well as Questions 2 and 3, are summarized below:
Details of the Stormwater and S&EC plan were provided as Appendix C of the
Stormwater Management Report in the initial submittal (Erosion and Sediment
Control plan is Appendix C of Appendix C). This response provides additional
information requested by the Department, primarily contained in the attached April
24, 2025 Addendum-01 to Archdale Storm Water Management Report for Erosion
Control Enhancements, Kings Mountain Mining Project.
The project is essentially divided into 4 phases, discussed below.
Phase 1 — Site preparation
E&SC measures consist only of silt fence placed on downhill gradients during site
preparation of the NPI, Growth Media Stockpile, and the Contact Water Pond and
Sediment Pond areas. These measures are depicted on Figures E5 and E6. During
site preparation, the Growth Media Stockpile will be constructed as surface material
is removed for infrastructure to be constructed in Phase 2.
Stormwater from areas outside the existing pit will be discharged through Outfalls
001, 004, and 005 as identified in Figures E1 and E2.
Within the existing pit, stormwater will continue to be collected and pumped from
lower basins to a rock check dam with discharge occurring at Temporary Outfall
004.
Phase 2 — Facility Construction
The silt fencing installed in Phase 1 and depicted in Figures E5 and E6 will remain
and provide erosion control during construction of the facility outside of the TSF
structure, which will remain in place until disturbed areas are re-stabilized.
Stabilization of the Growth Media Stockpile will occur immediately after Phase 1
construction is complete. At this point Outfall 005 will no longer have regulated
stormwater contributing to it.
Access roads, and construction of the Contact Water Pond and Sediment Pond
basins will begin to manage stormwater runoff from affected areas outside the
existing pit.

Construction of the TSF structure will occur in a pre-existing internally-draining pit
with no runoff. Stormwater and sediment collected in the pit will be managed as it
currently is (i.e., collected in areas internal to the TSF excavation, pumped to the
existing sediment check dam discharge location, identified as Outfall 004).
Phase 3 Operations
Sediment ponds will provide erosion control for actively disturbed areas of the
facility, specifically the TSF and the perimeter roads.
• Stormwater from the TSF drainage basin (surface stormwater and underdrain
collection) will be collected in the TSF sump and pumped to the Contact
Water Pond, which will provide sedimentation control and surge capacity.
The CWP will be drained via a skimmer and discharge at Outfall 002.
• Water from perimeter haul roads will be directed to the Sedimentation Pond,
and discharged to Outfall 003
Other stormwater drainage from the facility will be from unaffected or stabilized
areas, and not require sedimentation control other than typical stormwater BMPs
such as outlet protection. Discharge points from these areas is represented by
Outfalls 001 and 005. Note that outfall 005 was added as DEMLR comments to
address the flows
Phase 4 — Closure
At closure, the growth media stockpile will be consumed for closure cover. The TSF
will be stabilized consistent with the reclamation plan, and surface runoff will be
collected and routed through existing channels. The CWP, and sediment ponds will
be breached to allow normal Stormwater flow through them.
2. Show the drainage areas and applicable calculations for each basin.
Calculations do not appear to have been provided in the submittal.
Response: Information is provided in the attached memo and figures.
3. Include E&SC measures for the entire site, including the growth media
stockpile. Offsite drainage into the growth media area is not adequately
addressed.
Response: The revised memo and figures incorporate stormwater management and
erosion and sediment control around the growth media stockpile, and incorporates
management of offsite drainage onto the site.
The erosion and sediment control measures to be employed during construction are
typical down-slope silt fence and straw wattle combinations. The growth media pile
will be created early in the construction phase, and will be immediately reseeded

for stabilization. Once stabilization has been achieved, no erosion and sediment
control measures will be necessary.
4. The drawings (ex. Figure 17) appear to show multiple new culverts being
installed under I-85 and discharging on the southeast side of I-85. Provide
design information for these culverts and documentation that any needed
permissions to install such culverts have been obtained.
Response: There will be no new culverts being installed under I-85. There are 3
proposed new culverts to be built on the site, but these will discharge to culverts
already present under I-85 to convey stormwater to the same unnamed tributary
as they currently do. Figures El-E6 were enhanced to more clearly identify new vs.
existing culverts.
5. Mine reclamation techniques should be included on a reclamation map,
showing the techniques used for each portion of the mine. The text
includes a very detailed reclamation plan, but no details are shown on the
drawings.
Response: Figure 23 (Sequence Map: End of Reclamation at the Archdale TSF) has
been updated and included as an attachment to include reclamation closure method
tasks for specific marked areas of the project.
The reclamation closure techniques and methods identified on this figure correlate
to the D1, D3, or D4 letter designations that are further described below and in
Section D. (Reclamation Plan) of the Supplemental Report:
D1a: Dismantle base drain and tailings surface stormwater collection sumps and
remove from site.
D1b: Minor regrading of the compacted tailings to create a mounded surface with
2:1 slopes that drain storm water to the TSF perimeter channel. A minimum of 12"
of closure cover will be placed followed by a minimum of 12" of growth media.
D1c: Immediately install BMPs, including hydroseeding with approved permanent
seed mix (Table 9), coir matting, slope protections, create berms and channels to
convey storm water to the established perimeter channels. Stormwater controls
are described in Appendix B of Appendix K of Supplemental Report.
D1d: Plant tree seedings on the tailings surface and some reclaimed roads.
D1e,f,g: Remove all recyclable materials, equipment and structures in the non-
process infrastructure (NPI) areas. Concrete foundations and floor slabs will be
rubbleized and placed in the contact water transfer pond void or disposed offsite at
an approved location. Identify, sample, and dispose of any potentially impacted
soils from construction equipment, if needed.

D1h: Regrade NPI areas to pre-existing topography and convey storm water to
existing culverts under I-85. Place 12" of growth media, cast approved permanent
seed mix to revegetate surfaces.
D1i: Breach and remove collection and sediment ponds after closure cover
placement to convey discharges to existing drainages. Remove all culverts that
were installed during the TSF Project.
D1j: Remove seepage collection tank and fill void with rock. Grade surface to direct
stormwater to existing culvert under I-85.
D1k: Manage stormwater from the TSF using the diversion channels constructed at
the toe of the embankment (see updated Figure 23 and existing Figures 24, 25, and
32) to convey a probable maximum precipitation storm event. Place riprap along
channels where high water velocities could result in erosion (see Detail 3 in Figure
32 for riprap information). Channel reconfiguration details are in Appendix K and
shown in Figure 32.
D11: Reclaim transfer water pond after revegetation has occurred and stormwater
channels have been reconfigured for closure. Remove pond liner and fill void with
rock or approved materials.
D1m: Remove culverts located east and west of the contact water transfer pond to
re-establish the original surface water flow towards I-85. Remove other culverts
and the drop inlet installed near the sediment basin during construction and replac
with a swale that allows vehicular access after closure.
D1o: Electrical systems may be required to supply energy to support post-closure
land use. Once there is no need for energy onsite, this infrastructure will be
decommissioned and removed.
D1p: Remove pipes and pumps once the water supply to the Project is no longer
needed. Buried pipelines may be capped and left in place.
D1q: Reclaim the 100-foot perimeter haul road to a 15-foot wide post-closure road
for maintenance (Figure 32). Establish a closure perimeter channel to manage
stormwater. Prepare reclaimed roads for revegetation by adding growth media, as
needed. Reclaim outer side of perimeter roads as it is narrowed along the toe of
slopes, and as surface water channels are widened.
D3a: Install barricades at the site entrances to prohibit public entry.
D4a: All growth media (from the GMS area), overburden, soils bank, and base
materials at the Project will be used to reclaim the entire TSF Scarify all remaining
exposed areas and revegetate with an approved seed mix.

6. A meeting with the regional staff to review the E&SC drawings and scheme
is recommended prior to submitting additional information.
Response: The consultation process between Albemarle and MRO staff has been
extremely helpful during the development of the drawings and is reflected in the
materials provided in this response. Albemarle is always willing to continue
consultation as needed to ensure our response adequately addresses DEMLR's
requirements.

ATTACHMENT C
Technical Memorandum: Addendum-01 to Archdale Storm Water
Management Report for Erosion Control Enhancements, Kings Mountain
Mining Project

srk consulting 525 Suitonsulting(U.S.),Inc.
� 5250 Neil Road,Suite 300
Reno,NV 89502
United States
T:[phone]
F:[phone]
[e-mail]
www.srk.com
Technical Memorandum
To: John Kuhn Date: April 24, 2025
Company: Albermarle From: Gary Hurban
Subject: Addendum-01 to Archdale Storm Water Project#: USPR002033
Management Report for Erosion Control
Enhancements, Kings Mountain Mining
Project
SRK Consulting Inc. (U.S.) (SRK) was retained by Albermarle Corporation to make enhancements
to erosion and sediment control figures in the report - Archdale Storm Water Management Report,
Kings Mountain Project, North Carolina, Rev02, dated April 15, 2024 (Archdale SW report). The
enhancements and clarifications are to address review comments from North Carolina Department
of Environmental Quality(NC DEQ), Division of Energy, Mineral and land Resources (DEMLR). This
technical memorandum (memo) is provided as Addendum-01 to the above report to document the
work and additional calculations performed to address DEMLR comments; neither SRK nor
Albemarle plan to reissue the actual Archdale SW report.
1 Scope of Memo
The Archdale SW report was developed to support the Pre-Feasibility Study Environmental
Assessment (EA) for the Kings Mountain Mining Project (Project). The Project includes the mine
facilities near Kings Mountain, and the filtered tailings storage facility (dry stack TSF) at the Archdale
site. The Archdale SW report was prepared per guidance documents including the North Carolina
Surface Mining Manual (DEHNR, 1996), the Global Industry Standard on Tailings Management
(GISTM, 2020), and the Erosion and Sediment Control Planning and Design Manual (NCDEQ,
2013).
The following sections in the Archdale SW report remain unchanged:
- Executive Summary
- Section 1 — Introduction
- Section 2 — Site Environment
- Sections 3.1, 3.2, 3.3 and 3.7 in Surface Water Controls (Section 3)
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This memo documents additional stormwater controls for a Growth Media Stockpile (GMS) and thus
adds elements to the channel layout in Section 3.4, and hydrologic and hydraulic analysis in Section
3.5 of the Archdale SW report.
This memo also provides clarification on sedimentation controls discussed in Section 3.6 —
Sedimentation Controls, in the Archdale SW report, and in the erosion control plan in Appendix C -
Development and Operational Erosion and Sediment Control Plan, Kings Mountain Mining Project,
April 4, 2024 (ESC plan).
2 Design Criteria
Table 3-1 in the Archdale SW report, and Table 2.1 in the ESC plan, list the design storm criteria for
various surface water controls at the site and is reproduced below.
Table 2.1: Archdale Design Storm Criteria (per Archdale SW report and ESC plan)
Recommended by NC Mining Manual
Infrastructure (1996)
Project Design Criteria And Erosion and Sediment Control
Type Planning
and Design Manual NC
Permanent Channels PMP Local storm 10-year storm (temporary)
adjacent to the TSF 25- ear storm permanent
Permanent Channels 10-year storm (temporary)
in the Non-Process 100-year Storm 25-year storm (permanent)
Area
Culverts PMP Local storm 25- ear storm
25-year storm for all
sediment
Ponds control ponds 10-year storm (<20 acres)
100% containment of the 25-year storm ((>20 acres)
PMP storm event for TSF
Contact Pond
These criteria remain unchanged with the addition of the following criteria for specific sediment
controls.
3 Modifications to Sediment Controls
The following is a summary of improvements, clarifications and modifications made to the surface
water control designs - Sections 3.4 and 3.5 in Archdale SW report, and sedimentation controls -
Section 3.6, in Archdale SW report, per this memo:
- Figures 3-1 through 3-3 in the Archdale SW report have been replaced with Figures E1
through E11, included in Attachment 1. These include, but not limited to:
o Catchments were defined and color coded for clarity
o Permitted and temporary outfalls were illustrated
o Flow arrows were illustrated in each catchment for clarity
o The Q,o and Q25 were added to the tables on Figures E3 and E4
o A general construction sequence was added to Figure E3
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o A table of GMS non-contact water channels was added to Figure E10
o Additional details for Riprap Apron, Temporary Gravel Construction Entrance, Anti-
Seep Collar and Sediment Basin with Riser plan and profile were added to Figure
E11
- Surface water control channels, a culvert and erosion control measures were included for
the GMS.
- The Sediment Pond was enlarged to manage the 25-year, 24-hour design storm instead of
the 10-year, 24-hour design storm included in original report.
- NC-CULVERT-TPAD2 was increased in size from an 18-inch culvert to a 30-inch culvert.
- The Contact Pond and Sediment Pond was redesigned as Riser Basins instead of as
Skimmer Basins.
- Tabular summaries of required design criteria and adequate, selected design parameters
used in the designs for the Contact Pond and Sediment Pond were included on Figure E9.
3.1 Growth Media Stockpile Stormwater Channels
Following completion of the Archdale SW report, a GMSt was added to the Archdale design as part
of closure planning. The GMS is to store growth media for closure cover that will be salvaged from
the NPI pad and TSF perimeter road footprints at beginning of mine construction. Hydrologic and
hydraulic analyses were performed to locate and size surface water controls for the GMS and are
discussed below.
The same USDA SCS methods used for rainfall-runoff modeling in the Archdale SW report were
employed to estimate peak flow rates for surface water controls for the GMS. Because of the simple
hydrologic network of catchments at the GMS, i.e., hydrologic routing was not required and less than
ten (10) subbasins were needed, the Win TR-55 program, developed by USDA-NRCS (2002) was
used to estimate peak flow rates for the GMS channels instead of an HEC-HMS hydrologic model.
Catchments C1 through C7 and Offsite 6a were delineated for the GMS as shown in Figure 3.1
below, and on Figures E3 through E6 in Attachment 1.
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LEGEND '�
NCG02 OUTFALL
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eqNCRETE PRE-Fas`:`�:��:�:}:.:..:....:..:..:..:..:..:..:...........:....::.....:..:..:.....:..:..:.. .:..:..:..:.....:.....:..:..:.....:..:.....:..:..
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---- - 005 TEMPORARY -
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Figure 3.1: Growth Media Stockpile Catchments
The Curve Numbers (CN values) for offsite catchments to estimate the peak flow were selected
based on land use classifications and corresponding Hydrologic Soil Groups, in accordance with
USDA TR-55 — Small Watershed Hydrology guidelines (USDA, 1986). All catchments (Cl through
C8)were classified as Hydrologic Soil Group B, based on the USDA soil report for Cleveland County,
North Carolina, (USDA, 2019) accessed by the USDA Web Soil Survey website.
For Catchment C1, a weighted average CN of 82 was calculated using combined land use types of
"newly graded area" for the concrete prefabrication facility area, and "meadow — continuous grass
(non-grazed)" for the interspersed grass areas. Catchments C2, C3, and C8 are dense forested
areas and were assigned CN values (refer Table 3.2) based on land use classifications of"woods"
or a "woods-grass" combination. A CN value of 81 was applied to Catchments C4 through C7, using
a land use classification of"row crops, straight row" to represent the coarse, uncompacted nature of
the stockpile surface slopes.
Time of concentration (Tc) was calculated using the NRCS Velocity Method (USDA-NRCS, 1997).
The hydrologic parameters and peak flow rates for each catchment are shown in Table 3.2.
Supporting calculations for CN and Tc are included in Attachment 2.
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Table 3.1: Hydrologic Parameters per Catchment
Drainage Curve Time of 25-year Storm
Catchment ID Area Number Concentration Peak Flow
(ac) (CN) (hrs) (cfs)
C 1 14.17 82 0.17 83.19
C2 2.99 58 0.18 7.88
C3 1.50 55 0.27 2.93
C4 0.81 81 0.10 5.24
C5 1.06 81 0.10 6.85
C6 1.88 81 0.10 12.12
C7 1.99 81 0.13 12.28
C8 0.44 58 0.10 1.30
The peak flow rates from the Win TR-55 model were used to size four stormwater channels around
the perimeter of the GMS and are shown on Figure 3.2, and Figure E7 in Attachment 1.
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LEGEND �. -
NCG02 OUTFACE ;'.r
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Figure 3.2: GMS Stormwater Channels and Culvert
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SRK Consulting Page 6
Manning's equation was used to size the channels for the 25-year, 24-hour storm event based on
normal depth and steady flow assumptions. All four channels are triangular (v-ditches) with a depth
of 2.5 feet, with 2.5H:1V sideslopes. Channel NC-C2 collects run-on from catchment C2 and runoff
from catchment C4. Channel NC-C3 is primarily to divert run-on from catchment C3 with runoff from
catchment C5 naturally flowing to the low point in the middle of the GMS, and a culvert which is
discussed further in the next section.
Channel armoring requirements were evaluated based on North Carolina maximum permissible
velocity criteria, i.e., grass-lined channels must have a velocity less than 5 ft./sec.; channels with a
velocity higher than 5 ft./sec. need to utilize rock riprap or another suitable armoring alternative. All
channels have velocities greater than 5 ft./sec. so the use of riprap D5o was calculated using the
Federal Highways Administration (FHA) HEC-15 methodology. Channel dimensions and channel
armoring requirements for each channel are shown in Table 3.2; supporting calculations are included
in Attachment 2.
Table 3.2: GMS Stormwater Channel Specifications
Peak Channel Flow Channel Channel Riprap Riprap
Channel ContributingSlope Freeboard Slope Size Thickness
Flow m i n. Depth max. Velocity 5o . x5o
ID Catchment(s) ( ) (max.) (D ) (15D )
(cfs) (%) (ft) (ft) (%) (ft/sec) (in) (in)
NC-C2 C2+C4 13.1 2.4 1.2 1.3 9.9 6.52 9 14
NC-C3 C3+C5 9.8 1.0 1.2 1.3 9.5 6.06 9 14
NC-C6 C6 12.1 1.6 1.2 1.3 5.7 5.20 9 14
NC-C7 C7 12.3 1.0 1.3 1.2 11.9 6.87 12 18
3.2 Culvert Updates
The general slope of native topography in the GMS and Archdale area from North to South requires
a culvert to convey flow from upstream catchments (C1 through C5) to the 005 Temporary Outfall.
The HY-8 program (FHA, 2022) was used to size a 30-inch diameter RCP culvert as shown on
Figure 3.2, and in Figures in Attachment 1. The culvert is located at the low point of native
topography on the North side of the GMS. Flow is routed to the culvert via stormwater channels NC-
C2 and NC-C3 and by native topography. Because the GMS is temporary feature, the culvert is
designed for the 10-year, 24-hour storm event peak flow rate of 82 cfs. Supporting culvert
calculations are included in Attachment 2.
Culvert NC-CULVERT-TPAD2 was reviewed and found to be undersized as an 18-inch diameter
culvert. This culvert is upsized to a 30-inch diameter corrugated steel pipe (CSP). Supporting culvert
calculations are included in Attachment 2.
3.3 Contact and Sediment Pond Design Modifications
The Contact Water Pond (Contact Pond) and Sediment Pond were originally designed with a 10-
year, 24-hour design storm and as "Skimmer basins" in the Archdale SW report. Per the NC Erosion
GH/BK KM_Memo_Addendum ArchdaleSurfWtrRpt_20250424_fnl.docx April 24,2025

SRK Consulting Page 7
and Sediment Control Planning and Design Manual(NCDEQ, 2013), if the sediment basin has a life
of more than three years then the design storm is the 25-year, 24-hour storm. In addition, if a
sediment basin has a contributing area of greater than 10 acres, it must be designed as a "Riser
basin" instead of a Skimmer basin. Tables 3.6 and 3.7 in the Archdale SW report for the Sediment
and Contact Pond volumes and parameters are replaced with Table 3.3 and Table 3.4, respectively;
note that parameters modified are indicated in bold text. These tables and modifications are also
included in the updated figures on Figure E10, in Attachment 1.
Table 3.3: Sediment Pond Volume and Parameters
Parameter Value Required
Contributing Watershed ac 64.0 Maximum 100 ac
Assumed Disturbed Area ac 64.0
Q25 Inflow to Pond cfs 88
Top Width ft 100
Top Length ft 460
Crest Elevation ft 880
Length to Width Ratio 4.6 Minimum 2:1, Maximum 6:1
Pond Depth 15 Minimum 2 ft
Pond Slopes H:V 2:1
Bottom Elevation ft 865
Baffles 3
Emergency Spillway Invert ft 876.5
Depth of Spillway ft 3.5 Minimum 2 ft
Area at Spillway Invert ac 0.88 0.88 ac
Volume at Spillway ac ft 7.18 2.64 ac ft
Emergency Spillway Width ft 50
Principal Spillway(Riser) Elev
ft amsl 875.5
Riser Size in 36
Barrel Size in 24
Skimmer Size in 6
Head on Orifice ft 0.42
Average Skimmer Flow m 214
Orifice Diameter in 5.25
Time to Dewater days 2.8 Minimum 2 days
Updated value denoted in BOLD
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Table 3.4: Contact Pond Volume and Parameters
Parameter Value Required
Contributing Watershed ac 82.6 Maximum 100 ac
Assumed Disturbed Area ac 82.6
Q25 Inflow to Pond cfs 17.2
Top Width ft 140
Top Length ft 400
Crest Elevation ft 902.5
Length to Width Ratio 2.9 Minimum 2:1, Maximum 6:1
Pond Depth ft 12.5 Minimum 2 ft
Pond Slopes H:V 2:1
Bottom Elevation ft 890
Baffles 3
Emergency Spillway Invert ft 899
Depth to Spillway ft 3.5 Minimum 2 ft
Area at Spillway ac 1.12 0.17 ac
Volume at Spillway ac ft 8.28 3.41 ac ft
Principal Spillway(Riser)(el.
amsl) 898
Riser Size in 18
Barrel Size in 6
Skimmer Size in 8
Head on Orifice 0.5
Average Skimmer Flow m 275.8
Orifice Diameter in 5.75
Time to Dewater(days) 2.8 Minimum 2 days
Updated value denoted in BOLD
Sediment Pond Riser Pipe and Barrel
The difference between a Skimmer basin and a Riser basin is the inclusion of a Riser pipe and barrel
pipe as the principal spillway.
The NCDEQ spreadsheet "Sediment Basin Spreadsheet" was used to size the riser pipe and barrel
diameters for the Sediment Pond. This includes sizing the riser/barrel combination to pass the 2-
year, 24-hour storm peak flow rate. The 2-year storm inflow rate to the Sediment Pond was
calculated using the HEC-HMS model from the Archdale SW report by adding a model simulation
for the 2-year storm event. The 2-year storm peak flow rate of 39 cfs can be passed with a 36-inch
diameter riser pipe attached to a 24-inch barrel. The storm surcharge with this configuration is 1 foot
and sets the top elevation of the riser pipe at 875.5 feet above mean sea level (amsl), i.e., 1 foot
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SRK Consulting Page 9
below the emergency spillway elevation of 876.5 feet amsl (Figure 3.3). Supporting data for the 2-
year flow rate and riser and barrel calculations are included in Attachment 2.
10'
880' amsl
h-y 35 T
876.5' amsl _-____E'_T1°` ............. T 4.5'
1.0'
15' ��-
�875.5'amsl
3'
IL
Figure 3.3: Sediment Pond Schematic Outlet Dimensions
Contact Pond Spillway, Riser Pipe and Barrel
The Contact Water Management Pond (Contact Pond) is not a "typical" sediment pond because it
does not have a natural upstream catchment contributing inflow to the pond. As discussed in Section
3.4.3 of the Archdale SW report, contact water will be pumped from the TSF temporary surface water
sumps on the active TSF surface, and from seepage collection sumps at the base of the TSF. A
maximum pumping rate of 1,250 gpm, or 2.8 cfs, is planned to empty the PMF from the TSF surface
in less than two weeks. The maximum inflow rate to the Contact Pond is therefore the 2.8 cfs inflow
from pumping, plus the direct precipitation to the pond. The direct precipitation to the pond for the
PMP is modeled in the HEC-HMS model as 14.4 cfs, for a total maximum inflow rate to the pond of
17.2 cfs.
A 30-inch RCP culvert with anti-seep collars is included as the emergency spillway for the Contact
Pond. An HY-8 culvert analysis for the PMP inflow rate of 17.2 cfs has 2.2 feet of headwater and
thus meets the minimum 1 foot of freeboard to the crest of the pond.
For the riser pipe and barrel calculations, the 2-year flow rate from direct precipitation to the pond is
modeled in the HEC-HMS model as 1.9 cfs, for a total maximum inflow rate to the pond of 4.7 cfs.
This flow can be passed with an 18-inch diameter riser pipe attached to a 6-inch barrel. The storm
surcharge with this configuration is 1 foot and sets the top elevation of the riser pipe at 898 feet
above mean sea level (amsl), i.e., 1 foot below the invert elevation of the 30-inch culvert spillway
(Figure 3.3). Supporting data for the 2-year flow rate and barrel calculations are included in
Attachment 2.
3'
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SRK Consulting Page 10
10'
902.5' amsl _,F
3.5'
SolhMay
899' amsl ------E�'�`�"-`-�..... .......... T 4.5'
1.01
12.5
898' amsl
18"
6"
Figure 3.4: Contact Pond Schematic Outlet Dimensions
Skimmer Dewatering Calculations
Both ponds also have skimmer systems to drain the basins form the top where the water has the
least amount of suspended sediment. The skimmer system for each pond is specified to dewater the
basin in approximately 2.8 days, which exceeds the minimum drainage time of 2 days (48 hours).
The skimmer dewatering calculations were revised to use the NCDEQ ES&C design spreadsheet
titled "Sediment Control Measures with Skimmer Dewatering Calculation" for dewatering time
calculations and are calculated using the required basin volume and not the design basin volume.
The Sediment Pond will employ a 6-inch skimmer with a 5.25-inch orifice size. The Contact Pond
will employ an 8-inch skimmer with a 5.75-inch orifice size. Supporting calculations are included in
Attachment 2.
3.4 Erosion and Sediment Control Measures
The ESC plan (Appendix C) of the Archdale SW report includes the sediment and erosion controls
below in regular text, with additional items included per this memo in bold text:
• Sediment pond control with skimmer
• Culvert outlet stabilization with Riprap Apron Calculations
• Permanent grass-lined channels
• Permanent riprap-lined channels
• Temporary silt fences
• Level spreaders
• Rock check dams
• Compost socks or straw wattles
• Temporary gravel construction entrance
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Figure C-2 in the ESC plan has been replaced with Figures E4, E5, E6 and E7 showing locations
of erosion and sediment controls at Archdale.
Section 4 of the ESC plan (Appendix C of Archdale SW report) outlines the anticipated construction
schedule for the Archdale site facilities.
Section 4.1 of the ESC plan summarizes Site Preparation activities; Section 4.1.1 is Topsoil Salvage
and Unsuitable Soil Removal, which includes clearing and grubbing of vegetation and then salvage
of growth media. The change to this section is the addition of the GMS and the stormwater controls
designed and is discussed in Section 3.1 above. The Contact Pond and Sediment Pond will be
constructed as part of the cut and fill grading activities. Because the drainage patterns will change
on nearly a daily basis during cut and fill grading, care will be taken to grade areas to temporary
sediment traps below areas where flow concentrates (where flow paths are convergent); areas that
will sheet flow, where flow paths are divergent, will flow toward silt fences. The sediment traps will
be adjusted daily as construction progresses.
Section 4.2 of the ESC plan summarizes Facility Construction. The update to this section is a
correction only - the Contact Pond was originally designed at 12.5 feet deep with 2H:1V sideslopes,
instead of the 15 feet deep with 2.5H:1 V sideslopes.
Further updates to the ESC plan include,
1) the addition of compost socks (or straw wattles) on cut slopes, fill slopes and the slopes
of the GMS stockpile to facilitate vegetation growth (Figures E3 through E7),
2) a detail added to Figure Ell showing dimensions and material for a temporary
construction entrance/exit, and
3) riprap apron calculations for D5o, riprap thickness, and length and width dimensions for
each apron per peak flow rate and culvert size; calculations are included in Attachment
2.
Regards
SRK Consulting (U.S.), Inc.
This signs ure was scanned with the
outho ' approval or iusi a i
this nt; us is not
a t ize .
Gary Hurban
Principal Consultant- Engineering
GH/BK KM_Memo_Addend um Arch daleSurfWtrRpt_20250424_fnl.docx April 24,2025

SRK
s rk consulting Ren Consulting(U.S.),Inc.
5250 Neil Road,Suite 300
Reno,NV 89502
United States
T:[phone]
F:[phone]
[e-mail]
www.srk.com
Attachment 1 : Figures E1 through E11
GH/BK KM_Memo_Addendum ArchdaleSurfWtrRpt_20250424_fnl.docx April 24,2025

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REVISIONS DESIGN:GH REVIEWED: DPH PREPARED BY: DRAWING TITLE: ISSUE:
REV. DESCRIPTION DATE DRAWN:BK APPROVED:GH FINAL
A RESPONSE TO AGENCY COMMENTS O4.24.2025 srk consultingDATE:
COORDINATE SYSTEM: � EXISTING CONDTIONS, WEST SIDE
04.24.2025
NC STATE PLANE NAD83 FT SRK PROJECT Ni REVISION:
PREPARED FOR:
PROJECT: USPR002033 A
KINGS MOUNTAIN MINE PRELIMINARY ARCHDALE DRAWING NO.
J� ALBEMARLE Operated by. STORM WATER MANAGEMENT PLAN
IF THE ABOVE BAR DOES NOT MEASURE 1 INCH, Albemarle-Lithium FIGURE El
KINGS MOUNTAIN MINE PROJECT
FILE NAME: USPR000576-Channel layout_Jan2025.dwg
THE DRAWING SCALE IS ALTERED
C:\Users\bkemeh\SRK Consulting\NA USPR002033 Albemarle Corporation-Kings Mountain Permitting Support-0300—Hydrology\040—Drafting\USPR000576-Channel layout—Jan21