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Home My WebLink AboutNCG021045_Archdale_StormwaterManagement_20240815 Archdale Storm Water Management Report Kings Mountain Mining Project North Carolina Rev02 Report Date: April 15, 2024 Report Prepared for A ALBEMARLE" Albemarle Corporation 4250 Congress Street Charlotte, NC 28209 Report Prepared by $; enm consulting SRK Consulting (U.S.), Inc. 999 171" Street, Suite 400 Denver, CO 80202 SRK Project Number: USPR000576 Albemarle Document Number: KM60-EN-RP-9498 North Carolina Firm License Number: C-5030 Author: David Hoekstra, BS, PE, NCEES, SME-RM Reviewed by: Mauricio Herrera, PhD, P.Eng. SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page i Executive Summary A surface water management plan for the Archdale TSF component of the Kings Mountain Mining Project (KMMP or Project) has been developed in support of the Pre-Feasibility Study Environmental Assessment (EA) application. The water management system was prepared for the proposed life of mine, including construction, operation with reclamation, decommissioning and reclamation. Design criteria have been selected based on applicable regulations and associated guidance documents, including the North Carolina Surface Mining Manual (1996), the Global Industry Standard on Tailings Management (GISTM, 2020) Flood Design Criteria, and with consideration for Project-specific risks. The objectives of the water management system include minimizing the potential effects on the downstream environment by managing water within the Project footprint such that water quality and water quantity objectives are achieved, and to limit the loss of production due to damage from storm events. The principal philosophy of the Archdale TSF Water Management plan is to separate clean, non-contact water from water that has come into contact with tailings disposal activities. Non-contact water is collected in separate surface water diversion structures, managed with appropriate erosion and sediment controls, and released to existing drainages at or near to the pre-development discharge points. Contact water is separately collected in a series of channels and contact water management ponds, with all water detained and monitored before being released to an Unnamed Tributary of Dixon Branch (designated as Archdale Creek)when it meets the appropriate water quality. Design criteria for the Project have been selected to meet or exceed the requirements of the North Carolina Surface Mining Manual (February 1996) and the Erosion and Sediment Control Planning and Design Manual for North Carolina (May 2013). The selected criteria and the North Carolina recommendations are shown in Table ES-1 below: Table ES-1: Surface Water Design Criteria Recommended by NC Mining Manual (1996) Infrastructure Type Project Design Criteria And Erosion and Sediment Control Planning and Design Manual NC Permanent Channels PMP Local storm 10-year storm (temporary) adjacent to the TSF 25- ear storm (permanent) Permanent Channels in the Non-Process 100 year Storm 10-year storm (temporary) 25-year storm (permanent) Area Culverts PMP Local storm 25-year 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 Collection Pond The perimeter channel around the TSF will utilize a composite channel design, with a low-flow triangular channel section adjacent to the TSF Perimeter berm and a minimum 50-ft perimeter roadway sloping towards the low flow channel at 2%. The low flow portion of the channel will be designed to convey the flow from the 100 year, 24 hour storm event and utilize the 50 ft wide roadway to convey flows higher than that up to the PMP event. Freeboard for the low-flow channel will be provided by the additional 1 ft of flow available on the MH/MW Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page ii roadway, and a minimum 18-inch high safety berm will provide freeboard above the roadway surface at the PMP design flow. Non-contact perimeter channels are designed to route run-off from undisturbed areas around project infrastructure into Archdale Creek, maintaining clean water clean. Erosion protection for channels was selected based on the maximum tributary catchment throughout the life of the Project, and the expected velocities during design flood events. Most of the channels are grass-lined, while those segments with steeper gradient are lined with riprap. One sediment control pond will be situated downstream of the TSF perimeter channels to manage non-contact water from the active TSF Perimeter corridor before discharging into Archdale Creek. Non-contact water collected from areas in the non-process infrastructure components of the Archdale site will be revegetated or resurfaced during the initial development stage and will only require sediment controls during the facility construction. Once the surfaces have stabilized, non-contact water from these areas will be conveyed through the Project site and released to Archdale Creek without additional sediment control requirement. M H/M W Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx Ap ri 1 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page i Table of Contents ExecutiveSummary........................................................................................................... i 1 Introduction.................................................................................................................. 4 1.1 Property Location................................................................................................................................4 1.2 Property History ..................................................................................................................................6 1.3 Project Overview.................................................................................................................................6 1.4 Project Layout.....................................................................................................................................7 2 Site Environment ......................................................................................................... 8 2.1 General Description ............................................................................................................................8 2.2 Climate................................................................................................................................................8 2.2.1 Temperature............................................................................................................................8 2.2.2 Evaporation .............................................................................................................................8 2.2.3 Precipitation.............................................................................................................................9 2.2.4 Storm Frequency...................................................................................................................10 2.3 Wind Patterns....................................................................................................................................12 2.4 Surface Water Conditions.................................................................................................................12 2.4.1 Topography...........................................................................................................................12 2.4.2 Existing Drainage Network....................................................................................................12 2.4.3 Floodplains............................................................................................................................15 2.4.4 Surface Water Streamflow Monitoring ..................................................................................15 2.4.5 Baseflow Estimates...............................................................................................................15 3 Surface Water Controls ............................................................................................. 17 3.1 Design Objectives.............................................................................................................................17 3.2 Design Criteria ..................................................................................................................................17 3.2.1 NC Surface Mining Manual (1996)........................................................................................17 3.2.2 Project Adopted Criteria........................................................................................................18 3.3 Methodology......................................................................................................................................18 3.3.1 HEC-HMS Software ..............................................................................................................18 3.3.2 Hydrologic Methodology........................................................................................................19 3.3.3 Hydraulic Methodology..........................................................................................................21 3.4 Conceptual Channel Network...........................................................................................................21 3.4.1 Active TSF Perimeter............................................................................................................21 3.4.2 NPI Pad .................................................................................................................................22 3.4.3 Active TSF Areas ..................................................................................................................22 3.4.4 Final Channel Layout ............................................................................................................24 3.5 Design of Surface Water Controls ....................................................................................................26 DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page ii 3.5.1 Channel Design.....................................................................................................................26 3.6 Sedimentation Controls.....................................................................................................................27 3.6.1 Perimeter Sediment Control Pond ........................................................................................28 3.6.2 TSF Collection Pond .............................................................................................................28 3.7 Surface Water Controls Quantities ...................................................................................................29 4 Conclusions ............................................................................................................... 32 5 References.................................................................................................................. 33 Disclaimer........................................................................................................................ 34 Copyright ......................................................................................................................... 34 List of Tables Table 3-1: Project Design Criteria for Surface Water Infrastructure.................................................................18 Table3-2: CN Values .......................................................................................................................................19 Table 3-3: TSF Perimeter Non-Contact Water Composite Channels ..............................................................26 Table 3-4: NPI Non-Contact Water Channels ..................................................................................................27 Table3-5: Culvert Crossings............................................................................................................................27 Table 3-6: TSF Sediment Pond Volume and Surface Areas............................................................................28 Table 3-7: TSF Collection Ponds Volumes and Surface Areas........................................................................29 Table 3-8: Surface Water Management Quantities..........................................................................................30 List of Figures Figure1-1: Location Map....................................................................................................................................5 Figure 1-2: Preliminary Kings Mountain Mining Project Archdale Site Map.......................................................7 Figure 2-1: Average Monthly Evaporation..........................................................................................................9 Figure 2-2: Annual Precipitation and Distribution of Monthly Precipitation ......................................................10 Figure 2-3: Excerpted Tables showing Site-Specific Study and Annual Return Intervals Results...................11 Figure 2-4: Wind Rose Data in the Vicinity of Kings Mountain.........................................................................12 Figure 2-5: Kings Creek Watershed .................................................................................................................13 Figure 2-6: Extent of Detailed Topography for the Study Area ........................................................................14 Figure 2-7: Existing Streamflow Network .........................................................................................................15 Figure 2-8: FEMA Flood Plain Map ..................................................................................................................16 Figure 3-1: Archdale Watershed Upstream of Interstate Hwy 85 and Model Sub-catchments........................20 Figure 3-2: Typical Schematic of the Tailings Storage Facility Perimeter Channel Configuration...................23 Figure3-3: Final Channel Layout.....................................................................................................................25 DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page iii Appendices Appendix D-1: UT to Dixon Branch Stability Assessment Appendix D-2: Channel Design Calculations Appendix D-3: Erosion and Sediment Control Plan DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 4 1 Introduction Kings Mountain Mining Project(KMMP or Project) is a legacy open pit lithium mining operation located in the city of Kings Mountain, North Carolina, in the southeastern United States.The Project is a lithium pegmatite deposit that is currently being investigated for redevelopment by Albemarle Corporation (Albemarle)as part of a prefeasibility-level analysis. Albemarle commissioned SRK Consulting (U.S.), Inc. (SRK) to develop prefeasibility level designs for an expansion of the existing pit, waste rock management, water management, and ancillary infrastructure to aid Albemarle in making informed decisions concerning advancement of the Project. The Project will generate tailings material that will be disposed of at a remote site approximately 3 miles south of the Kings Mountain Project at the proposed Archdale Tailings Storage Facility (TSF). As part of this study, SRK Consulting (U.S.), Inc. (SRK) is developing a PFS surface water design of stormwater management channels, detention and retention ponds, sediment control structures, and spillways that meet the required design criteria for each facility,which were selected using a risk-based approach. This document is intended to support mine, discharge, stormwater, and dam safety permitting from components of this project, as well as contribute to the Environmental assessment of the site. 1.1 Property Location Situated in Cleveland County, the mine is approximately 35 miles west of Charlotte, North Carolina. Located amidst rolling hills of the Piedmont Plateau, the Project is in a predominantly rural setting within the city of Kings Mountain. The mine site covers a significant land area, which includes both the proposed extraction areas and associated processing infrastructure. Figure 1-1 shows the location of the mine and the location of the Archdale TSF. D H/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx Ap ri 1 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 5 Galax -- '1 91—Ridge �. Perkway (a21} 1 � r251 ICI ICI �� Statesville Asheville 5—Lh Maaresville Mounu ns ja^ie Land �aae North CafdI11na 73 pp c' Green River —` Shelby i r — rr'' ,ze, Spartanburg Wade++amp[an � �Ro[k NIII ❑ GreerMlle yet } South Carolina � a S 79 i5 20 Mr. Source: ESRI,2023(modified by SRK) Figure 1-1: Location Map D H/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx Ap ri 12024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 6 1.2 Property History The following summary highlights the history of KMMP, compiled from records available to SRK: • Mining started in 1883 with the discovery of cassiterite, a tin-bearing mineral, within the outcropping pegmatites. • Subsequently, open pit mining for tin occurred sporadically between 1903 and 1937 (Horton and Butler, 1988). • Between 1943 and 1945, under the sponsorship of the U.S. government, Solvay established a processing plant and mined for spodumene from the outcropping pegmatites(Garrett,2004). • In the early 1950s, Foote, a subsidiary of Newmont Mining Corporation, purchased the property and began open pit mining (assumed at the beginning of 1955)and extracting lithium from the spodumene. • In 1993, exploration and mining operations ceased when the open pit bottom reached approximately 660 feet(ft) above mean sea level (amsl). • In early 1994, an open pit lake started to form due to rebounding groundwater, and the pit lake reached an elevation of 817 ft amsl (as of January 2023). • During the groundwater recovery period (1994 to present), water was sporadically pumped from Kings Mountain pit lake to a nearby quarry (Martin Marietta)to support quarry operation. • Albemarle acquired the site in 2015, resuming exploration and mine development activities. The proposed Archdale Tailings Storage Facility(TSF)will be located at the site of a former mica mine. The following summary of the Site is compiled from records available to SRK: • The site was formerly owned by the Kings Mountain Mica Company, which began operation in 1949. • The site was owned by several different companies between 1994 and 2021, including Franklin Minerals, Oglebay Norton, Zemex, General Chemical and Imerys. • Imerys expanded mining to the property north of the Archdale site across Highway 29 in 2011 • Albemarle acquired the site in 2023 for use as a permanent storage of filtered tailings from the Kings Mountain Lithium project. Available aerial photography of the Site suggests that mining activities continued through about 2013. The current site layout encompasses several shallow in-pit ponds formed during the previous mica mining operations. Figure 1-2 shows a detailed map of the current site layout. 1.3 Project Overview Tailings from the spodumene concentrate process at KMMP will be filtered to approximately 10 to 15% moisture content by weight and transported off-site to the proposed Archdale TSF for disposal. A portion of the waste rock mined at KMMP will be transported to Archdale for construction of the TSF embankment. An initial TSF embankment will be constructed on-site to hold approximately one to two years of filtered tailings. Thereafter, filtered tailings material will be placed and compacted with mobile equipment at the same time that the TSF perimeter embankment is raised with compacted waste rock and/or fill. The TSF will be constructed in this manner until the facility reaches its capacity of 9.16 million tons. At which time, the facility will be closed and reclaimed. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 7 1.4 Project Layout The Project layout and the relative locations of the major components of the Project are shown in Figure 1-2.The Project is bounded by Interstate 85 on the south and Highway 29 on the north.Access to the TSF will be from Highway 29 with separate truck and light vehicle entrances. The proposed Archdale Site (Site) will include a small office and maintenance facilities, parking, water storage and sediment control facilities as part of the Non-Process Infrastructure(NPI), and a TSF perimeter access road. Spaces for a small road base stockpile and a growth media storage area are included in the site plan. SFTE ENTRANCE - 1WFT_PFRIMETER HIGH POINT HAUUACCESSROAD FILTERED TAILIN,-S STORA.GE LIGHT VEHICLE ENTRANCE Y EMEAN KMENT CREST .^. CREST 96060 EIEti.anal / I SEEPAGEI ERCEPTIONDRAIN PERIMETER ACCESS ROAD WATERAND SEWER MAIN LIGHT`JEHICLE ACCESS ROAD > _ '\ EXISTING CULVERTS(TYRI PROPOSED CULVERT(TYP.} /. SEDIMENT BASINS FUEL PAD / /f SEEPAGE COLLECTI—INK MAINTENANCE SHOP T CULVERT ABLE TO PASS PMP PROPERTY BOUNDARY /1 V' �.—- OVERHEAD POWER }V / CONTACT WATER POND GROWTH MEDIA 5 f STOCKPILE{-200L CY'sl / LAY➢OWN AREA TRUCKPARKING PARKING Source:SRK 2023 Figure 1-2: Preliminary Kings Mountain Mining Project Archdale Site Map DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 8 2 Site Environment 2.1 General Description The Project is located in southwestern North Carolina, USA, adjacent to the city of Kings Mountain on the Interstate 85(1-85)transit corridor, approximately 36 miles west of the city of Charlotte(Figure 1-1). The property is located at approximately 35 degrees (°), 11 minutes north latitude and 81 o, 24 minutes west longitude. 2.2 Climate The Project is situated within the Koppen-Geiger Cfa climate classification (Kottek, 2006), which describes a continental type of climate without a dry season.Temperatures during the warmest months are above 72 degrees Fahrenheit(°F), and temperatures in the coldest months are between 27°F and 65°F. Average monthly precipitation varies between 3 and 5 inches. Average annual precipitation is 42 inches, with an even distribution of rainfall throughout the year, and an average annual snowfall of 4 inches. Southwestern North Carolina is prone to thunderstorms during the summer and ice storms during the winter. 2.2.1 Temperature The climate of the Project vicinity is humid subtropical with hot summers and mild winters.The monthly temperature ranges from a minimum of around YF in January to a maximum of around 104°F in August,with an average temperature of around 60°F. Legacy data show that temperatures in the area have been increasing, with an average rise of 0.3°F per decade since 1970, or roughly 1.7°F from 1895 to 2020. Climate change is expected to further contribute to this warming trend, potentially impacting surface water conditions, such as increased evaporation rates and altered streamflow patterns. Predictive climate models suggest further warming in the future, potentially resulting in more frequent and severe heatwaves and droughts. 2.2.2 Evaporation Evaporation rates at the Project vary based on temperature, humidity levels, wind speed, and solar radiation. Legacy data show that evaporation rates are highest in summer, averaging around 6 to 7 inches per month, and lowest in winter, with around 2 to 3 inches per month (Figure 2-1). Overall, average annual evaporation ranges from 54 to 58 inches. Evaporation impacts surface water availability by contributing to water loss from lakes, rivers, and streams. Factors such as vegetation cover, land use practices, and soil moisture levels influence evaporation variability. Climate models predict that evaporation rates will continue to increase in the future due to warming temperatures and changes in precipitation patterns. D H/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx Ap ri 1 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 9 S 7 6 0 5 Y o a 4 7 W s 3 r o 1 0 January February March April May June July August September October November December Clemson Univ Chesnee 7 WSW Chapel Hill 2 W — — —Average Gold Sim Source:SRK Figure 2-1: Average Monthly Evaporation 2.2.3 Precipitation Precipitation totals at the Project vary throughout the year. Based on the last 30 years, the area typically receives between 51 to 60 inches of rainfall annually (Figure 2-2), with precipitation being distributed relatively evenly throughout the year without a clear wet or dry season. The region is susceptible to extreme precipitation events, such as tropical storms and hurricanes, which can bring heavy rainfall and cause flooding. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 10 Distribution of Precipitation 80 70 v to — L N � 8 - o .a 5 40 - a 30 20 o ¢` 10 a p January February ma h April May June July Augu t 5eptember October November December Annual Total 2.59G5% 5%-30% ■1D%-25% ■25%-SD% ■Median ■50%-75% ■75%-90% ■9D%-95% 95%-97.5% Annual Precipitation ao lu — r 60 c 50 Y 40 i 30 20 0 1925 1930 1935 1940 1945 1950 1955 1%0 1%5 1970 1925 19 0 199i 1990 1195 2000 2005 2010 2015 2020 Source:SRK Figure 2-2: Annual Precipitation and Distribution of Monthly Precipitation 2.2.4 Storm Frequency Storms encountered at the Project vary in frequency and intensity throughout the year. For example, a 100 year, 24-hour storm event produces, on average, 7.96 inches of precipitation (National Oceanic and Atmospheric Administration (NOAA), 2023). The region experiences thunderstorms, tropical storms, and hurricanes, which can bring heavy rainfall and high winds. Thunderstorms, which are the most common type of storm in the area, see peak activity in July and August. Factors such as temperature, humidity, wind patterns, and topography influence storm occurrence. These storms can impact surface water availability and quality by causing flooding, erosion, and sedimentation. Climate change could increase the frequency and intensity of storms in the future, posing higher risks of flooding and erosion. Applied Weather Associates (AWA) completed the Site-Specific Probable Maximum Precipitation Study for Kings Mountain Mining Operations, North Carolina(AWA,2022)for the Kings Mountain basin in North Carolina. AWA utilized a storm-based approach to derive the site-specific probable maximum precipitation (PMP) depths to update the PMP depths originally developed in hydrometeorological reports developed by the National Weather Service. Figure 2-3 shows Tables 10.4 and 10.5 excerpted from AWA (2022), which show the results of the site-specific study with annual return intervals to 1:10,000 years and beyond. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report-Kings Mountain Page 11 Table 10.4: King% Mountain basin AEP for 6-,24-,and 72-hour P IP Kings Mountain AEP Estimate PM P(in) AEP ARI 6hr 28.5 2.5Y9 39,829,769 24hr 32.4 1.09'7 9,144,104 72hr 32.4 3.93'7 2,540,551 Table 10.5, Kings Mountain hstsin a.erall frequency analysis for 6,24-,and 72-hour Kings Mnt Frequency Analysis 6-hour 24-hour 72-hour ARI AEP AEP 50% 5% 95% 50% 5% 95% 5096 5% 95% 1.01 0.99010 9.9-1 1.0 0.9 1.1 2A 1.8 2.2 2.4 2.2 2.6 2 0_SO000 5.0'1 2.3 2.1 23 3.6 3.4 3.9 43 4.0 4.6 5 0.20000 2.0" 3.2 2.9 3A 4A 4.4 5.1 5.7 5.2 6.1 10 0.10000 1.0', 3.8 3.5 4A 5.5 5.1 6.0 6.6 6.1 7.1 25 0.04000 4.0 4.7 4.3 5A 6.6 6.1 7.2 7.9 7.3 8.5 50 0.02000 2.0 5.3 4.9 5.8 7.5 6.9 8.2 8_9 8.2 9.7 100 0.01000 1.0-1 6.0 5.5 63 8A 7.7 9.2 9.9 9.1 10.9 200 0.00500 5.0'} 6.9 6.2 7A 93 8.5 10A 11.0 10.1 123 500 0.0a200 2.0" 7A 7.1 a 10.6 9.6 12A 12.6 11.4 14.3 1,000 0.oama 1.0', 8.7 7.8 10A 11.7 10A 13.5 13.9 12.4 16A 5,000 0.00020 2.04 10.9 9.5 13.1 14.4 12.5 17.2 17.1 14.9 20A 10,000 0.00010 1.04 11.9 10.3 14.5 15.7 13.5 19.1 18.6 16.0 22.6 100,00o 0.00001 1.0', 15.9 13.1 20.5 20.4 16.9 26.S 24.2 20.0 31.3 1,000,000 0.000001 1.0', 20.5 16.3 25.3 26.2 20.7 36.1 31.0 24.5 423 10,000,000 0.0000001 1.0', 26.2 19.9 38.7 33.1 25.0 48.8 39.1 29.7 57A 100,000,000 OM000001 1.0', 33.1 24.0 52.5 41.3 29.9 65.5 48.9 95.4 77A 1,000,000,000 0.000000001 1.0'4 41.4 29.6 70.7 51.2 35.3 97A 60.6 41.9 103.5 10,000,000,000 0.0000000001 i0.10 51.4 33.9 94.7 63.1 41.5 116.1 74.7 49.2 137.5 Source:AWA,2022 Figure 2-3: Excerpted Tables showing Site-Specific Study and Annual Return Intervals Results AWA (2022) also included a site-specific climate change assessment to "understand and quantify whether the climate change projections related to temperature, moisture, and precipitation are expected to change significantly in the future (through 2100), and whether those changes would warrant a change to the currently derived PMP depths."The results of the study indicate "an increase in precipitation and temperature in the future" with "the most likely outcome regarding precipitation over the basin going forward is that the mean annual and seasonal amount will increase, but the individual extreme events will stay within the range of uncertainty currently calculated" (AWA, 2022). The site-specific water balance prepared to inform water management requirements across the site considers the results of the site-specific climate study and is described in detail in SRK's Technical Report 2022 Prefeasibility Study, Surface Water: Water Balance Development(SRK, 2023a). DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 12 2.3 Wind Patterns Wind rose data were obtained from the Department of Environmental Quality (DEQ)Air Quality Portal available online at https://airquality.climate.ncsu.edu/wind/. Figure 2-4 presents wind rose data for the Shelby Municipal Airport, located about 13 miles west of Kings Mountain, and for the Gastonia Municipal Airport, located about 13 miles east of Kings Mountain. The data for both sites indicate the predominant wind direction is out of the north and northeast, with a good portion of the winds out of the south and southwest. Em Wind rose for KAKH in Gastonia,NC Wind rose for KEHO in Shelby,NC For Feb 1.1999 m May 24 2023191%o!darn availeblel For Jan 3,200A m May 24,2@3 93%of date available) N N 75 71 _.. \ NE .. \ ENE WNW -1- W — ■ E W E 111 Calm Windsl¢mphl: ssw 5sF 551N nE 39 21 of observations $ Calm W nds I4 mphl: S 35Wa d observations Wind Speed: �i mph mpeM1 �15 mph s �J uu Wind Speed: •sto7mpn 1omim n •>=_mmph �,ma„esu. „ vas mpn mph lsmzo mpn ,u �5m7 mph 10 to 15mph >_20 mph Source: DEQ Air Quality Portal, https://airquality.climate.ncsu.edu/wind/ Figure 2-4: Wind Rose Data in the Vicinity of Kings Mountain 2.4 Surface Water Conditions The project is located within the Dixon Branch watershed, a tributary to Kings Creek which is part of the Broad River basin which stretches from western North Carolina into northwestern South Carolina (Figure 2-5)and encompasses a total 1,513 square miles. The headwaters originate in the Blue Ridge Mountains and generally flow southeastward ly. The basin has a varied landscape of forested land, pasture and row crop agricultural land, and urban land and is made up of 17 sub-watersheds, including Kings Creek. 2.4.1 Topography Detailed topography of the Project area at 1 ft contour intervals was provided by Albemarle for the Project site in AutoCAD .dwg format. This topographic base map was used to delineate watersheds and establish channel grading in subsequent calculations. Figure 2-6 shows the extent of the detailed topography available at 5 ft intervals and the property boundary of the Project area. 2.4.2 Existing Drainage Network The natural drainage network in the vicinity of the Project is heavily influenced by legacy and active mining activities. The contributing watersheds to the Project area are roughly defined by Highway 29 DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 13 to the north and east and Highway 85 to the South.The site has no well-defined drainage due to legacy mining activities, but discharges from the Site would flow into the Dixon Branch drainage, as shown in Figure 2-7. For the sake of clarity,this document refers to the Unnamed Tributary(UT)of Dixon Branch that carries the discharges from the Archdale property as "Archdale Creek". i . lil M.�.+u.i Mt*Y.eYF��• I�WSY• n•• ••• M� f � • ti +f { � KnQS Voun�n Lfn rq Prised i• kr{h{ldl�Tdillnq� � Stara a Facility f ' ilrF k }X�I l ' rw.a.. L ' 1 x •y+ {M 4, n.awi. "C a ns+ NDTES I IN unity me n Fnelem Lviei5 aftemrse OE 1U00 " N 40M 4 a= Sources:SRK, USGS Figure 2-5: Kings Creek Watershed DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 14 PO �—1 Q0 _ P� �O �O O�. �XI LNIS r v ��nmi na�x,,,xn„nwl in n ........... n .;oyphynn SOUTH BATTLEGROUND AVE._ _ Wr , f -= --- -- --tNTERSrATE65-__ PROPERTY LINE t Source:GPI,2023 Figure 2-6: Extent of Detailed Topography for the Study Area D H/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx Ap ri 12024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 15 't -ARC14DALE PROPERTY 1_ BOUNDARY r :r CULVERTS UNDER ROADWAY F U J 6 O Q i �1�55 GaEEK Source:SRK,2024 Figure 2-7: Existing Streamflow Network 2.4.3 Floodplains Flood plain mapping for the Project area was obtained from the Federal Emergency Management Agency(FEMA) National Flood Hazard Layer(NFHL, 2023). The Flood Insurance Rate Map indicates there are no FEMA defined floodplains in the Project area (Figure 2-8). 2.4.4 Surface Water Streamflow Monitoring There are no existing streamflow monitoring points within the facility footprints, as the legacy mining operations have only discharged to Archdale creek by pumping from ponds within the pit footprints to the permitted discharge locations at the southern property limits. The nearest flow monitoring station is on Kings Creek at Blacksburg, SC; USGS ID 02153590 with a watershed of 27.9 square miles (USGS, 2024). 2.4.5 Baseflow Estimates A stability assessment of Archdale Creek (UT of Dixon Branch) drainage was performed by SWCA Environmental Consultants in January 2024 (SWCA, 2024) and is included as Appendix A. The drainage is located at the upper reaches of the watershed, and flow in the drainages is dominated by irregular pumping from the quarry, no discernable baseflow could be identified. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 16 6 r Col. A IL . . >r l �C - 'F�}i}• � ry Esri,USDA warm Service Agenc},-Mie-esc�L Powered 6y Esr. Appr000e m we3tida based m user apuy WI[holi[ease Flood flew[pa i6F El m.a reprrseM a CTnes SeUonS VaM 1%Annual Chance antl dnn nee naunrentanre SPECIAL FLO wllth 0;E or Dop<4 ar-° rialer5urraoe Elevabon PIN WAZARD AREAS A10rlomy Fao(.a":---...a.wu n..e — C-Dm WTmnsFladd eueS elan Ll ne iBF E7 9w4eledFbodraap9ouedar! ---_- LhnrtdSWdl 0.2%Am�I Chedee need Heeard.Anne* d�nlo.r.nnai.ba. plix.n U$d;ILr W Apo weh.-r.K lurndKllar'9auedAry K+btgnal haw maiable [lepin lescthanvneiv 4t w.th ara-.aie ---Cu.etel Tr�n l Bawd e ss areas d le than one square IwI..^--x ORER _ ,! Plaflle Basar..e MAP PANELS un.mappen Futwre Qmar m i%anlwar FEATURES Hpdrog nlh!IC Feature Chance Flood Hazard.:r:r i ®IIr a of I6nrr10 Hood H'=-'rd Ax x Area w rth Reduwd Flood Rack due to GENERAL --_' Ci.an"l,Culvert.or Storm Sewer gff.ev..Lnuns OTHER AREAS OF _&�-See%aim.z,,, STRUCTURES t 1 i I I l r Lr _Dire-w Fk"Id ll Area M undeeerllyded Mom Heard FLOOD HAMD Area wrh F load Rork due w Lnee_,o ` 6t?remu Peetee[ed Area OTHER AREAS®4Ca-t':? -Ag3pwrce°Jx:_•.•rea Figure 2-8: FEMA Flood Plain Map D H/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx Ap ri 12024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 17 3 Surface Water Controls 3.1 Design Objectives The objectives of the surface water management plan are: • To keep non-contact water clean by constructing diversion channels to divert non-contact water away from mine areas and to discharge into Archdale Creek • To collect and manage contact water prior to discharging into Archdale Creek 3.2 Design Criteria The following standards and guidelines apply with respect to surface water controls: • Surface Mining Manual. A Guide for Permitting, Operation, and Reclamation. State of North Carolina Department of Environment, Health, and Natural Resources. Division of Land Resources. Land Quality Section. February 1996 • Erosion and Sediment Control Planning and Design Manual. North Carolina. May 2013. North Carolina Sedimentation Control Commission, North Carolina Department of Environment and Natural Reserves, and the North Carolina Agricultural Extension Services • Global Industry Standard on Tailings Management(GISTM, 2020) Flood Design Criteria 3.2.1 NC Surface Mining Manual (1996) The NC Surface Mining Manual (1996) stipulates that: • Temporary diversions, those that function for less than a year, should be designed to carry at least the 10-year design storm for the total drainage area, furthermore: o Temporary diversions require erosion protection. Velocities over 2.5 ft per second may require a temporary liner with supporting design calculations unless the soil is especially erosion resistant. o Side slopes of the diversion berm should be constructed to a 2 horizontal to 1 vertical, or flatter. The slopes then should be immediately seeded. • Permanent ditches and channels, those constructed to function for more than a year and to carry concentrated runoff non-erosively to a predetermined destination, must be designed for the 25-year storm event for the total drainage area, furthermore: o Side slopes must be 2 horizontal to 1 vertical, or flatter. o Grass-lined channels are generally used for slopes less than 5%. o Velocities should not exceed 5 ft per second for established grass lined channels. o Sharp bends and turns should be avoided. o Velocities over the maximum allowable design velocity for grass lined channels require a permanent structural lining such as riprap. o In cases where velocity allows, riprap may be installed in the bottom of the channel with grass lined side slopes to decrease the quantity of riprap needed. Filter fabric or a 6 inch- deep sand gravel crushed stone filter must be installed under the riprap to prevent undermining. The filter should extend under the entire area of the riprap lining. o The receiving channel or outlet must be protected from erosion by ensuring that the outlet velocity is minimized. DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 18 o Outlet protection should be included if necessary. o Channels must be stabilized as soon as possible after construction, and sediment-laden runoff diverted away from stabilized channels. o Channels must be inspected after every major rainfall and appropriately repaired. 3.2.2 Project Adopted Criteria Project adopted criteria for the surface water infrastructure (channels, culverts and sediment ponds) that generally exceeded the recommendations of the NC Mining Manual are shown in Table 3-1. Table 3-1: Project Design Criteria for Surface Water Infrastructure Infrastructure Recommended by NC Mining Manual (1996) Type Project Design Criteria And Erosion and Sediment Control Planning and Design Manual NC Permanent Channels PMP Local storm 10-year storm (temporary) adjacent to the TSF 25- ear storm (permanent) Permanent Channels in 100 year Storm 10-year storm (temporary) the Non Process Area 25- ear storm (permanent) Culverts PMP Local storm 25-year 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 Collection Pond Source:SRK,2023 3.3 Methodology SRK incorporated a stormwater management approach of using run-off treatment; all disturbed areas are managed by sediment control measures, consisting of sediment mitigation at the source, and wet ponds or stormwater wetlands to manage discharges to the existing drainages. The contributing Dixon Branch watershed at the 1-85 culvert crossings is 190.1 acres, as shown in Figure 3-1. The watershed was further subdivided into smaller sub-catchments, delineated based on the developed mine condition, as well as per mine phases. Design rainfall was obtained from AWA (2022) as described in Section 2.2.4, and shown in as Figure 2-3. The design storm events were distributed temporally using the alternating block frequency distribution to provide a representative hyetograph(storm intensity over time)for each of the frequency events. The runoff produced by the increment change in rainfall produces a distribution of run-off over time, or hydrograph. A description of the methodology is presented below, and parameters and calculations are presented in Appendix B. 3.3.1 HEC-HMS Software Hydrologic modeling for the Project was developed using the Hydrologic Modeling System (HEC-HMS) software (USACE 2023). HEC-HMS is designed to simulate the precipitation-run-off processes of dendritic drainage basins. It is designed to be applicable in a wide range of geographic areas for solving the widest possible range of problems. This includes large river basin water supply and flood hydrology, and small urban or natural watershed run-off. DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 19 3.3.2 Hydrologic Methodology HEC-HMS includes a number of options for determining excess run-off from precipitation and lag and attenuation of the resulting hydrograph as it travels along the watershed surface and along defined flow paths. The model was configured to use the methodologies described below: Excess run-off is calculated for each sub-basin using the Curve Number (CN) Method (NRCS 2004), a well-established methodology with a large library of parameters for different vegetation, soil types and surface conditions. Table 3-2 presents the soil textures (USDA 2024) and CNs used for the individual surfaces within the model. For basins with multiple types of surfaces, the CN was developed by weighting the CNs by area. Existing conditions that would produce run-on to the property were limited to the areas northwest of the Site, while the remainder of the Project Site would consist of engineered surfaces. Table 3-2: CN Values Soil/Land Use Classification MUSYM CURVENO Water W 92 Hulett gravelly sandy loam, 8%to 15%slopes, stony HtC 72 Helena-Sed efield complex, 0%to 6%slopes HhB 84 Urban land Ur 92 Udorthents-Urban land complex, 1%to 15%slopes UdC 72 Madison gravelly sandy clay loam, 2 to 8 percent slopes, moderately eroded MaB2 72 Madison clay loam, 6%to 10%slopes, moderately eroded McC2 72 Appling sandy loam, 1 to 6 percent slopes A B 72 Filtered Tailings 60 Reclaimed Surfaces 76 Haul Road/Industrial Pad 82 Source:SRK,2024 Hydrograph Lag and Attenuation is calculated using the SCS Unit Hydrograph Method. The transformation of the unit hydrographs to the run-off hydrograph at the discharge point of the basin requires the time of concentration (Tc). This parameter is defined as the time required for run-off to travel from the hydraulically most distant point in the watershed to the outlet(NRCS, 2010). Tc was calculated using the Velocity Method, which assumes the Tc is the sum of the travel times for segments along the hydraulically most distanced flow path.The segments used in the velocity method may be of three types of flow; sheet flow, shallow concentrated flow, or open channel flow. Flows in defined channels may also be lagged and attenuated as they are routed through the channel network. The kinematic wave method (USACE 2019)was applied to flows that are routed through channels at the site in addition to the lag and attenuation calculated as part of the stream hydrograph calculation. DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 I LEGEND 0 100 200 400 LIGHT VEHICLE AND HAUL +HI+Hi}H}HH+}hHiiIIIIHFI+1+}FIIIIIIHHHIHHF i000 CONTOUR 25'(EXISTING) FEET VEHICLE SEPARATION BERM - 10O FT. PERIMETER CONTOUR 5'(EXISTING) HAUL/ ACCESS ROAD t000 CONTOUR 25'(PROPOSED) },+},+},+,�+►++}►+��++++}t►+}""+}f""+ all LIGHT VEHICLE ACCESS ---- (/ CONTOUR 5'(PROPOSED) -------------- WATER - - AND SEWER MAIN ---- ------------ . ------------------------- � PROPERTY BOUNDARY ------------------- o __ ----------------------------- -------------- Perim RAILWAY -- PAVED ROAD - - r SITE ENTRANCE DIRT ROAD 1 EDGE OF WATER L� IIIIII II U Offs ° ° FENCE PAVED DRAINAGE Ij POWER LINE 1 0 v rim 5 SEWER LINE 11 ----------- WATER LINE y.-Offsite 4 U Perim 8 BUILDING/PAD EXISTING BUILDING/PAD PROPOSED �I CULVERT EXISTING CULVERT PROPOSED II ` Perim-1 SUB-BASIN DELINEATION Offs 11i O ` I Perim 9 --- --_ -__ ---- --- / �1 Offsite 5 ��:=_-- -- - --- CutSlope 2 1 Pad 2 Pad 1 Cn Pad 3 PROPERTY BOUNDARY (D jj a w r__;b � Contact Pond o 0 D Q Pad 5 erim 1 Pad 7 Pad _ - _ O PARKING - - - Offsite 7 '�- Perim 2 erim 4 - ----------- , -------- �- Offsi 8 - - _ - - r - _ Perim 421 - _ \ o ------------ ------------ \ PMP EMERGENCY SPILLWAY EXISTING CULVERTS (TYP.) PERIMETER ACCESS ROAD ARCHDALE SUB-BASIN DELINEATIONS AND STARTER EMBANKMENT - PERIMETER ACCESS ROAD HIGH POINT (SCALE: 1" 200�> Archdale Sub-Basin Parameters Basin Area Composite Curve Total Lag (0.6*Tc) Total Travel Time SUBBASIN ID (sq mi) Number (min) (min) Contact Pond 0.003500 88 8.1 13.5 CutSlope 1 0.000797 76 4.2 7.1 CutSlope 2 0.000906 76 1.4 2.4 CutSlope 3 0.000453 76 0.8 1.4 Offsite 1 0.005094 74 6.4 10.7 Offsite 2 0.011813 72 0.8 1.4 Offsite 3 0.011656 72 3.3 5.5 Offsite 4 0.015313 72 1.3 2.1 Offsite 5 0.002297 72 5.2 8.7 Offsite 6 0.032016 72 2.8 4.7 Offsite 7 0.007984 72 5.8 9.6 Offsite 8 0.007313 73 20.8 34.6 Pad 1 0.002750 82 35.2 58.7 Pad 2 0.002109 82 33.4 55.7 Pad 3 0.001797 82 15.9 26.6 Pad 4 0.005391 82 23.5 39.2 Pad 5 0.000438 82 8.2 13.6 Pad 6 0.001422 82 10.3 17.2 Pad 7 0.000656 82 21.6 35.9 Perim 1 0.017921 77 2.1 3.5 Perim 2 0.007026 78 4.0 6.7 Perim 3 0.001326 81 3.4 5.7 Perim 4 0.003482 75 2.8 4.7 REVISIONS DESIGN:DPH REVIEWED:JO PREPARED BY: DRAWING TITLE: ISSUE: PERMIT Perim 5 0.017355 78 0.8 1.3 REV. DESCRIPTION DATE DRAWN:DPH APPROVED:JO Srk consultingARCHDALE STORM WATER BASIN DATE: Perim 6 0.008603 78 1.2 2.0 A SUBMITTED FOR CLIENT REVIEW 04.01.2024 0 ISSUED FOR PERMIT 04.15.2024 COORDINATE SYSTEM: DELINEATIONS 06.05.2024 Perim 7 0.021255 77 1.3 2.2 B RE-ISSUED FOR PERMITTING 06.05.2024 INC STATE PLANE NAD83 FT PREPARED FOR: SRK PROJECT NO.: REVISION: Perim 8 0.009055 78 1.0 1.6 PROJECT: USPR000576 B Perim 9 0.008243 78 1.5 2.5 KINGS MOUNTAIN MINE PRELIMINARY ARCHDALE DRAWING NO. DOES NOT MEASURE1INCH, Operated by: STORM WATER MANAGEMENT PLAN ALBEMARLE Albemarle-LithiumSed Pond 0.001094 93 20.4 34.1 IF THE ABOVE BAR J\ FIGURE 3-1 KINGS MOUNTAIN MINE PROJECT TSF 0.087933 60 0.0 0.0 FILE NAME: USPR000576-Channel layout REVB.dwg THE DRAWING SCALE IS ALTERED C:\Users\elynn\SRK Consulting\NA USPR000576 Albemarle Corporation Kings Mountain 2022 Pre Feasibility Study-0300_Hydrology\Flow Predictions\Archdale Surface Design Mar2024\USPR000576-Channel layout REVB.dwg SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 21 3.3.3 Hydraulic Methodology Using the peak flows determined by HEC-HMS as described above, the sizing and erosion protection for the channels were designed using a tabular spreadsheet to calculate various hydraulic parameters such as flow depth, velocity, erosive power, and hydraulic jump parameters. These hydraulic parameters were in turn used to size channels, estimate required erosion protection, and provide energy dissipation when necessary. Depth of flow and average channel velocity were calculated from flow rates using Manning's equation for normal depth. As the values of Manning's n roughness coefficients are variable within any given channel reach, flow velocity and flow depths were determined for low and high ranges of Manning's n values, respectively, and used appropriately in subsequent calculations. For example, when determining available freeboard in a channel, the high range of Manning's n was used to result in a higher estimate of flow depth.When determining erosion protection,the low range of Manning's n was used resulting in higher velocities. Channel depths were assigned to achieve a minimum acceptable freeboard in the channel. Freeboard was assumed to either be a minimum distance of 1 ft or '/2 of the velocity head in the channel. The velocity head is the conversion of all of the water's kinetic energy into potential energy. Channels that are susceptible to erosion from high velocity flows will be lined with rock armoring (riprap) to prevent erosion. The ability of riprap to resist erosive forces is determined by rock particle size, which was measured according to one of three methodologies, depending on the bed slope of the channel. • USACE Mild Slope Method — This method was developed for slopes flatter than 2% (USACE 1994) • USACE Steep Slope Method—This method was developed for channel beds steeper than 2% but less than 20% (USACE 1994) he riprap D50 is determined from the D30 using the method described in (Equation 17) • Robinson Design of Rock Chutes—Robinson (Robinson et al 1998)developed this method to size riprap for steep, rock lined chutes with slopes between 10% and 40%. Culverts were sized using the HY-8 software package (FHWA, 2021) 3.4 Conceptual Channel Network Non-contact surface water channels will be constructed during the development of the TSF to divert flows around the TSF infrastructure to collect surface run-off from these areas, preventing mixing with non-contact water. Channel networks are developed in three sections, each with a different water management approach. 3.4.1 Active TSF Perimeter Run-off from the active TSF perimeter will include haul roads, perimeter roads, concurrently reclaimed perimeter berms, and adjacent run-on areas. The design approach requires active sediment controls throughout the life of the facility to address run-off collected in the perimeter channel. The perimeter channel around the active TSF will utilize a composite channel design, with a low-flow triangular DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 22 channel section adjacent to the TSF Perimeter berm and a minimum 50-ft perimeter roadway sloping towards the low flow channel at 2%. A traffic safety berm at the outer edge of the perimeter road will be constructed to a minimum of 18-inch height. The low flow portion of the channel will be designed to convey the flow from the 100 year, 24 hour storm event and utilize the 50 ft wide roadway to convey flows higher than that up to the PMP event. The combined capacity of the triangular ditch and the roadway channel is sufficient to convey the PMF with 0.1 ft of freeboard on the roadway and the minimum 18-inch high safety berm will provide freeboard above the roadway surface at the PMP design flow. Any channels adjacent to the TSF perimeter, but not in the perimeter corridor, will be sized to convey the PMP flow with 1 ft of freeboard. This includes non-contact channels designed to divert off-site run- off around the TSF perimeter. The channels will slope from the northeast corner clockwise and counterclockwise to the southwest corner of the TSF. A typical section through the perimeter channel and haul road is shown in Detail 1 of Figure 3-2. A skimmer sediment pond will de-sediment the water before discharging it under Highway 85 through an existing 60 inches reinforced concrete pipe (RCP) culvert to Archdale Creek. 3.4.2 NPI Pad Run-off from the NPI areas will include access roads, parking and admin areas, workshops and office buildings, revegetated earthworks from the initial construction, impervious pad areas, and adjacent run-on areas. Channels and culverts in the NPI area will be designed to convey flows from the 100 year, 24 hour flood with 1 ft of freeboard. The design approach assigns best management practices (BMP) sediment controls to address runoff during the initial construction period only. Thereafter, channels and culverts capable of conveying the PMF are used to collect and divert run-off around or across the site without detention to discharge under Highway 85 through one of two existing RCP culverts (36 inches to the south and 30 inches to the east) into Archdale Creek. 3.4.3 Active TSF Areas Run-off from the active TSF surface within the crest of the perimeter berm is collected in a low point on the tailings against the perimeter berm and transferred to the Contact Water Management Pond as quickly as possible to avoid ponding on the TSF Surface (anticipated ponding time is less than 2 days for the 100 year storm event, as described in the Archdale Water Balance Report (SRK 2024). Additional flow is pumped from sumps at the base of the TSF to remove seepage from the filtered tailings and groundwater intercepted by the sump collection system. The Contact Water Management Pond was sized to detain contact water produced by the TSF up to the 100 year flood and convey flows from the PMF through an emergency spillway. If the water is acceptable quality for discharge, it will be discharged to the 30 inches RCP culvert under Highway 85 through a gravity pond skimmer or a pumping system utilizing a floating intake. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 TSF Perimeter Non-Contact Water Composite Channels NPI Area Non-Contact Water Channels 2.5 CONCURRENT RECLAMATION Channel Low Flow Channel Depth in Channel Bottom Channel Channel Riprap 1 Length Low Flow Depth Slope Riprap Size Roadway Length Side Width Depth Slope Size EMBANKMENT VARIES Design Design ROCK FILL Channel ID Event (ft) Side Slopes (ft) (%) (in) (ft) Channel ID Event (ft) Slopes (ft) (ft) (%) (in) (50FT. TO 10OFT) C STORMWATER DITCH (100-YR) � STORMWATER ROAD/DITCH (PMP) MIN 18" HIGH COMPACTED SOIL -PT11a PMF 2006 3HAV 2.25 0.43% None 1.02 NC-AR13a PMF 1836 3H:1V 4 2.50 0.53% None SEE TABLE FOR DIMENSIONS TRAFFIC SAFETY BERM C-PT11b PMF 1255 3H:1V 1.25 5.24% 14 0.30 NC-PAD1 100-yr 622 3H:1V 0 1.50 1.95% None C-PT11c PMF 555 31HAV 0.75 0.40% None 0.33 NC-PAD2 100-yr 680 3H:1V 0 1.50 1.89% None C-PT12a PMF 375 31HAV 1.00 0.52% None 0.47 NC-PAD3 100-yr 465 3H:1V 0 1.75 1.89% None 2.5 5 1 C-PT-12b PMF 1807 31HAV 1.75 1.14% None 0.77 NC-PAD4 100-yr 240 3H:1V 0 1.75 2.34% None C-PT12c PMF 611 3H:1V 2.00 0.85% None 0.97 NC-PAD5 100-yr 326 3H:1V 0 1.50 2.26% None PERIMETER ROAD i ROCK FILL C-PT12d PMF 1218 3HAV 2.50 1.02% None 1.10 NC-PAD6 100-yr 586 3H:1V 5 1.50 1.94% None C-PT12e PMF 532 31HAV 3.00 4.85% 32 0.43 NC-PAD7 100-yr 287 3H:1V 5 1.25 2.01% None C-PT-12f PMF 368 31HAV 3.00 2.31% 20 0.87 NC-PAD8 100-yr 251 3HAV 5 1.25 2.38% None 2FT FILTER SA NC-SWALE1 100-yr 40 10H:1V 2 1.50 2.38% None ND _ � 'T`\//�/%/%/%/%�%// \ \ \ \ \ \ \ 100- r NC-SWALE2 Y 180 10H:1 V 2 1.25 1.86% None Culvert Dimensions NC-SWALE3 100-yr 28 10H:1V 2 1.50 2.34% None EXISTING GROUND Culvert Culvert NC-SWALE4 PMP 391 10H:1V 2 2.00 2.58% None - - Design Number of Culvert Length Diameter Invert Slope Headwater NC-SWALE5 100-yr 403 10H:1V 2 1.50 2.34% None Culvert ID Event (ft) (in) Culverts Material (%) (ft) NC-DS1 100-yr 45 4H:1V 5 1.50 40.00% 9 Perim-Culvert PMP 60 18 4 RCP 0.0% 3.97 NC-BROW-T14a 100-yr 525 3H:1V 0 2.00 6.90% None 1 PERIMETER ROAD TYP. SECTION NC-CULV-TPAD1 100-YR 440 24 1 CSP 1.3% 4.00 NC-BROW-T14b 100-yr 620 3H:1V 0 2.00 8.90% None SCALE: 1"= 10' NC-CULV-TPAD2 PMP 470 18 1 CSP 3.3% 3.86 N7C-BROW-T14c 100-yr 467 3H:1V 0 2.00 6.13% None C-CULV-SPILLWAY PMP 325 30 1 CSP 6.2% 5.5 BOTTOM WIDTH 2.5 1 CONCURRENT RECLAMATION Level Spreader (not to scale) EMBANKMENT 50 FT. ROCK FILL /\DEPTH � BEEHIVE DROP INLET MIN 18" HIGH COMPACTED SOIL �; r -� ��' {'tN<<�•' �'��M. ��\ `\ \\ TRAFFIC SAFETY BERM �, : •� .�• ..,�• fit• ,, p,a..t•,1..,,�• .q„,.wll• /� /� \ 18"0 RCP CULVERT g a��•1 , °' ��'' �,- a. ,,....: Transition 2% ELEV. = 880' INLET IE= 876' diversion '`` �+'11"'� � • •� • to 4 grade .. �,, .nI„'101" .,F�\ �/'� ,,. �` `I ILL- SEE LINED CHANNEL ''1i�fawi••./`� ``�". ' `' 4 4'„r.+� " %• �,• SEE TABLES .3` ' ;ail•- s.�--��` u,. �.. 'rr` .t, I`' l� BELOW FOR SEDIMENTBASIN t��', !`!sIgl- �h° i� * : _ •�,4. N �v ��rl 1b ,1!` 1•. CHANNEL 'J�:,►at +1I11 •I1, ,r..�;�l�b;� DIMENSIONS 2 1 ` 'r;►,, r,-y� 1, .L4t 1,.,,{•'r'' t .� �� RIPRAP SIZE r•. .( �1 tll..ot-111 ' vit.r� `, r?• ti BOTTOM WIDTH 5 2FTFILTERSAND EXISTING GROUND \\,�\\ \ ��''; ,p►•�k.�'.!"*�N;ylH•^��;I�i',l-` .�tl�' `'' �� / �N"�' "t y �` Vd Stabilized (SEE TABLE) / / \\\\/�\\,�` fd1,�""M• ,,u• .gib.�. 1,1!• ,. •�11 ,.}4• ti. ,. ,�,.. �• ,ra i Q. �1�' u1t�� VAt a�''�' / �`' ,�� V slope ELEV. = 865' ,t. 1• �' 1 le I,7r4 Vi'\�� r ,,� J1� M'�� SIDE Stable �a �,� • �`'• , t �' ,�•. .. " t y' SLOPE undisturbed �� 4,. ,.1,`. 1+• �, , 4„• ' <<�, _. �a4• ..I / PERIMETER CORRIDOR CULVERT CROSSING Outlet ,� �I u,. q4. �� 1 0 o DEPTH \,�\ L SCALE: 1"= 10' �`'�'' 1 1 afi•• M�` � I+ 'Lt4. I" '` ,III AIL, �'' a!' ate• M.Ii• �u• ,Mh, �1• k"• •�\•� ,� �` �U �\ `� � � �` / l,l• k`• �' �Si' , Alt '"'Ir" w 1 tlk, 1 �, �+k"" FILTER FABRIC dl`, �I � �/ RIPRAP THICKNESS 1.5X A,1 ` , + 11••&, ��„ RIPRAP D50 ROAD o 0 0 �, ,'� „�„ �,( III wj, i �, Note: Contributing WIDTH o 0 0 0 o ti N� �M, ,` ,,<,I. ,<< 1 �I s watershed to level spreader RIPRAP CHANNEL 1�- �' not to exceed 5 ac. TYPICAL NPI DIVERSION CHANNEL DETAIL 4.5' o 0 0 0 0 6.5' Figure 6.40a Level spreader is designed to disperse small volumes of concentrated flow across stable slopes. NOT TO SCALE APPROACH _ _ _ _ _ _CORRUGATED STEEL DISCHARGE o 0 0 0 CHANNEL PIPE(CSP)CULVERT CHANNEL SEE TABLE � 0 Cross Section I Material Variable 3 OUTLET STABILIZATION stapled in dace 3 INLET STABILIZATION 3-2 SEE DETAIL p 3-2 SEE DETAIL 6 PLAN VIEW I min ROAD � Irt�II<< f 1 + t - FILTER FABRIC WIDTH Level lip Of s ,'eader _ ��` � � � I � � �j � {I�11�- t �--• I ' SAFETY TYPICAL OUTLET STABILIZATION DETAIL -� BERM 1 vvv ROAD FILL NOT TO SCALE Buried APPROACH - CHANNEL CORRUGATED STEEL � �� min �J PIPE CSP)CULVERT GRADE oU` DISCHARGE j\\ / CHANNEL DIAMETER /` Figure 6.40b Detail of level spreader cross section- (SEE TABLE) SOURCE: Erosion and Sediment Control Planning and Design Manual, North Carolina 3 INLET STABILIZATION SECTION VIEW 3 OUTLET STABILIZATION Department of Environmental and Natural Resources 3-2 3-2 SEE DETAIL SEE DETAIL TYPICAL LEVEL SPREADER DETAIL AND SECTION 6 TYPICAL CULVERT DETAIL SCALE: 1"= 10' NOT TO SCALE REVISIONS DESIGN:DPH REVIEWED:JO PREPARED BY: DRAWING TITLE: ISSUE: PERMIT REV. DESCRIPTION DATE DRAWN: DPH APPROVED:JO COORDINATE SYSTEM: � srk consultingSTORMWATER MANAGEMENT DETAILS A SUBMITTED FOR CLIENT REVIEW 04.01.2024 DATE: �0 ISSUED FOR PERMIT 04.15.2024 O4.15.2024 NC STATE PLANE NAD83 FT PREPARED FOR: SRK PROJECT NO.: REVISION: PROJECT: USPR000576 O KINGS MOUNTAIN MINI: PRELIMINARY ARCHDALE DRAWING NO. .,\ ALBEMARLE Operated by: STORM WATER MANAGEMENT PLAN IF THE ABOVE BAR Albemarle-Lithium FIGURE 3-2 DOESWINGSC NOT LEISAURE 1 TERNCH, KINGS MOUNTAIN MINE PROJECT FILE NAME: USPR000576-Channel layout REVO.dwg THE DRAWING SCALE IS ALTERED C:\Users\dhoekstra\SRK Consulting\NA USPR000576 Albemarle Corporation Kings Mountain 2022 Pre Feasibility Study-Internal\0300_Hydrology\Flow Predictions\Archdale Surface Design Mar2024\USPR000576-Channel layout REVO.dwg SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 24 3.4.4 Final Channel Layout Detailed perimeter sections, profiles, and plans of the TSF are presented in the Preliminary Archdale Tailings Storage Facility Design Drawing Package (SRK, 2024). Figure 3-3 shows the channel layout that will be constructed to provide surface water management control during operations. The channels were sized to safely convey the peak flow produced by the Probable Maximum Flood using the maximum catchments that will contribute to them during the operational period. Channels will be reconfigured during the closure period to address post-closure flows as described in the closure plan report provided separately (SRK 2024). DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 n a 0 100 200 400 LIGHT VEHICLE AND HAUL LEGEND FEET VEHICLE SEPARATION BERM i000 CONTOUR 25'(EXISTING) - ,+H++�++,++,+,+1,++,++�++ 100 FT. PERIMETER CONTOUR 5'(EXISTING) HAUL/ ACCESS ROAD t000 CONTOUR CONTOUR 55(PROPOSED)) �, LIGHT VEHICLE ACCESS ---- __ ------ - - WATER AND SEWER MAIN ------------------------ ° b� PROPERTY BOUNDARY - ------- o -------------- RAILWAY -------------� PERIMETER CHANNEL SECTION PAVED ROAD SITE ENTRANCE DIRT ROAD EDGE OF WATER L� �,IIIIII IIIII ii -d FENCE \7 - -------= 25+00 ---------------- q _ - - 30+00 `pry?C r=====_____' PAVED DRAINAGE C_ T12e I/ 35+00 POWER LINE 11 40+00 SEWER LINE I I j ?p10 11 \ ----------- WATER LINE q � I I I I 0 BUILDING/PAD EXISTING 1 BUILDING/PAD PROPOSED • ��'� EX-CULV-60" CULVERT EXISTING ltV -2 6 C-CULV-SPILLWY CULVERT PROPOSED NPI DIVERSIdN 5 SEE DETAIL 3-2 I + NC-SWALE4 CHANNEL SECTION 3-2 -> _> - DRAINAGE SWALE PROPOSED — _ 11 _ C-PT12a o _ CHANNEL PROPOSED 70. ow �1---PA_D2__ c� w II ■ Qom' — —> N�C-PAD ` PROPERTY BOUNDARY o` �I ® cn Ak CD ° ' 0 0 SXOO - NC- WALE o 0 NC-PAD6 E 52 C-PT1 +37 \ NC-PAD7 -S C'C, � 1 � a PARKING - - � - - ��q `D C-SPILL2 +00 C'ULv-0U-rj CD 00 0 X 15 < _ L (D < < — — C-PT11b o - r-==-===---- — — — — C-P T 11 C - LEVEL SPREADER 4 - - ----_______ LEVEL SPREADER SEE DETAIL 3-2 - SEE DETAIL o - - CULVERT TPAD-1 6 CULVERT SPILLWAY 6 SEE DETAIL 3-2 SEE DETAIL 3-2 PMP EMERGENCY SPILLWAY EXISTING CULVERTS (TYP.) PERIMETER ACCESS ROAD - AND STARTER EMBANKMENT FINAL TSF CHANNEL LAYOUT 2 PERIMETER CORRIDOR CULVERT CROSSING PERIMETER ACCESS ROAD HIGH POINT (SCALE: 1" =200') 3-2 Perimeter Corridor Composite Channel C-P 1100 1100 -,1050 � 1050 1000 _ — — - — _ = 1000 -0.50% _ -0.85% — J � — 950 950 — CPP� -PT12 - - r — - - - - - - - - - - - - - - - - - - o w a - - C-PT12a � - - ` - - - - - - — — — 900 w 900 y � - - - - — — - C-PT�2e - - - -L - - w 850 ` — — -PT12f - 850 0+00 1+00 2+0I.0 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11+00 12+00 13+00 14+00 15+00 16+00 17+00 18+00 19+00 20+00 21+00 22+00 23+00 24+00 25+00 26+00 27+00 28+00 29+00 30+00 31+00 32+00 33+00 34+00 35+00 36+00 37+00 38+00 39+00 40+00 41+00 42+00 43+00 44+00 45+00 46+00 47+00 48+00 49+00 50+00 51+00 52+00 53+00 54+00 STATION (FT.) PERIMETER CORRIDOR PROFILE ((COMPOSITE PERIMETER CHANNEL C-PT12) (SCALE: 1"=200') 1100 1100 -�1050 > 1050 J Z 1000 / — _ _ _ -1.01% U 1000 950 _ — — — — — 950 -PT11 w 900 — — — -5. ° - - - - — — — — — — — — — — — — -0.43% � 900 w 850 C-PT11 b — — _ — — — C-PT1 10 L— — — — — — — — 850 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11+00 12+00 13+00 14+00 15+00 16+00 17+00 18+00 19+00 20+00 21+00 22+00 23+00 24+00 25+00 26+00 27+00 28+00 29+00 30+00 31+00 32+00 33+00 34+00 35+00 36+00 37+00 38+00 39+00 STATION (FT.) PERIMETER CORRIDOR PROFILE (COMPOSITE PERIMETER CHANNEL C-PT11 ) (SCALE: 1" =200') REVISIONS DESIGN: DPH REVIEWED:JO PREPARED BY: DRAWING TITLE: ISSUE: PERMIT REV. DESCRIPTION DATE DRAWN:DPH APPROVED:JO � srk consulting A SUBMITTED FOR CLIENT REVIEW 04.01.2024 DATE: COORDINATE SYSTEM: � FINAL CHANNEL LAYOUT 06.05.2024 0 ISSUED FOR PERMIT 04.15.2024 B RE-ISSUED FOR PERMITTING 06.05.2024 NC STATE PLANE NAD83 FT PREPARED FOR: SRK PROJECT NO.: REVISION: PROJECT: USPR000576 B KINGS MOUNTAIN MINE PRELIMINARY ARCHDALE DRAWING NO. J\ ALBEMARLE Operated by. STORM WATER MANAGEMENT PLAN IF THE ABOVE BAR Albemarle-Lithium FIGURE 3-3 DOESWINGSC NOT LEISAURE 1 TERNCH, KINGS MOUNTAIN MINE PROJECT FILE NAME: USPR000576-Channel layout REVB.dwg THE DRAWING SCALE IS ALTERED C:\Users\elynn\SRK Consulting\NA USPR000576 Albemarle Corporation Kings Mountain 2022 Pre Feasibility Study-0300_Hydrology\Flow Predictions\Archdale Surface Design Mar2024\USPR000576-Channel layout REVB.dwg SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 26 3.5 Design of Surface Water Controls 3.5.1 Channel Design All channels were designed to safely convey the peak flow from the PMF, resulting from the Probable Maximum Precipitation (PMP) storm event from the maximum area that will contribute to them. The HEC-HMS model described in Section 3.4 was used to determine design peak flows for all channels identified in the conceptual streamflow network. These calculated flows, flow depths, and channel velocities were examined to iteratively adjust channel dimensions to arrive at acceptable hydraulic conditions. Where riprap calculations indicate riprap D5o dimensions above 9 inches, SRK recommends the use of Hydro Turf® (Watershed Geo, 2024) hardened erosion protection instead of riprap. Where riprap is recommended, a minimum thickness of D5o (mean particle size) x 2 is recommended based on USACE riprap design guidance (USACE 1994). Dimensions and calculated hydraulic parameters for the non-contact water channels are shown in Table 3-3: for the TSF perimeter composite channels and Table 3-4 for the NPI non-contact water channels. Table 3-5 presents a summary of the culvert crossings required where the channel network must cross under perimeter and haul roads that have been identified at this stage of the Project. The CWMP was designed to detain the PMF from the TSF surface storm event on the TSF, as well as seepage flows from the TSF sumps. The pond is sized to retain the volume from the 100-year storm event below the emergency spillway and discharge through the skimmer outlet. Flows in excess of the 100 year flood event up to the PMF will be discharged through the emergency spillway, consisting of a 30 inches corrugated metal pipe (CMP) culvert discharging to the 30 inches RCP culvert under Highway 85. Table 3-3: TSF Perimeter Non-Contact Water Composite Channels Channel Design Channel Low Flow Low Flow Channel Riprap Depth in ID Event Length Side Depth Slope D50 Size Roadway (ft) Slopes (ft) (%) (in) (ft) C-PT11a PMF 2006 3H:1V 2.25 0.43% None 1.02 C-PT11 b PMF 1255 3H:1V 1.25 5.24% hydroturf 0.30 C-PT11c PMF 555 3H:1V 0.75 0.40% None 0.33 C-PT12a PMF 375 3H:1V 1.00 0.52% None 0.47 C-PT-12b PMF 1807 3H:1V 1.75 1.14% None 0.77 C-PT12c PMF 611 3H:1V 2.00 0.85% None 0.97 C-PT12d PMF 1218 3H:1V 2.50 1.02% None 1.10 C-PT12e PMF 532 3H:1V 3.00 4.85% hydroturf 0.43 C-PT-12f PMF 368 3H:1V 3.00 2.31% hydroturf 0.87 Source:SRK,2024 DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 27 Table 3-4: NPI Non-Contact Water Channels Channel Bottom Channel Channel Riprap Channel ID Design Length Side Width Depth Slope Size Event ft Slopes ft ft % in NC-AR13a PMF 1836 3HAV 4 2.50 0.53% None NC-PAD1 100 year 622 3HAV 0 1.50 1.95% None NC-PAD2 100 year 680 3HAV 0 1.50 1.89% None NC-PAD3 100 year 465 3HAV 0 1.75 1.89% None NC-PAD4 100 year 240 3HAV 0 1.75 2.34% None NC-PAD5 100 year 326 3HAV 0 1.50 2.26% None NC-PAD6 100 year 586 3HAV 5 1.50 1.94% None NC-PAD7 100 year 287 3HAV 5 1.25 2.01% None NC-PAD8 100 year 251 3HAV 5 1.25 2.38% None NC-SWALE1 100 year 40 10HAV 2 1.50 2.38% None NC-SWALE2 100 year 180 10HAV 2 1.25 1.86% None NC-SWALE3 100 year 28 10HAV 2 1.50 2.34% None NC-SWALE4 PMP 391 10HAV 2 2.00 2.58% None NC-SWALE5 100 year 403 10HAV 2 1.50 2.34% None NC-DS1 100 year 45 4HAV 5 1.50 40.00% 9 NC-BROW-T14a 100 year 525 3HAV 0 2.00 6.90% None NC-BROW-T14b 100 year 620 3HAV 0 2.00 8.90% None NC-BROW-T14c 100 year 467 3HAV 0 2.00 6.13% None Source:SRK,2024 Table 3-5: Culvert Crossings Design Culvert Culvert Number Invert Culvert ID Event Length Diameter ol Culvert Slope Headwater (ft) (in) Culverts Material (%) (ft) Perim-Culvert PMP 60 18 4 RCP 0.0% 3.97 NC-CULV-TPAD1 100 year 440 24 1 CSP 1.3% 4.00 NC-CULV-TPAD2 PMP 4701 18 1 CSP 3.3% 3.86 C-CULV-SPILLWAY PMP 325 30 1 CSP 6.2% 5.5 Source:SRK,2024 3.6 Sedimentation Controls Ongoing sediment controls will be provided over the life of the facility by constructing a sediment control pond that will receive non-contact water flows from disturbed and undisturbed natural ground collected by the perimeter channels. The sediment ponds will discharge directly to Archdale Creek. Construction sediment controls will be provided during the active construction phase of the Project. BMP will be put into place to minimize the generation and transportation of sediment laded water during the development of the site. A site-specific Erosion and Sediment Control Plan has been developed for the Archdale site and is included as Appendix C. The majority of the sediment controls will be implemented during the construction of the TSF, while ongoing tailings placement, embankment raises, and concurrent reclamation will require on-going sediment controls over the life of the facility. Key components of the plan include the Perimeter Sediment Pond and the Contact Water Management Pond, described below. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 28 3.6.1 Perimeter Sediment Control Pond Surface run-off from all the non-contact areas in the Project area will be collected and routed to the sediment control pond. Table 3-6 presents a summary of the sediment ponds with their main characteristics. According to the North Carolina Sediment and Erosion Control Manual (2013), the following design criteria applies to sediment basins (ponds) in order to settle the 40-micron particle with a minimum efficiency of at least 70% during the 2-yr peak runoff event.: The minimum basin volume is to be determined based on 1,800 ft' of storage per acre of disturbed land. • The minimum surface area is to be determined based on 425 ft2 per cfs of the 10-year peak flow. At a minimum, design the combined spillway system for the sediment basin to be capable of passing the 25-year storm event for the total drainage area. The minimum dewatering time for the pond is 48 hours and will require 3 baffles unless less than 20 ft long. The Archdale Perimeter Sediment Pond will receive run-off from up to 65 acres of disturbed land, which includes perimeter roads and berms, haul roads and other mine disturbed areas. The location of the pond is shown in Figure 3-3 and will be configured as a skimmer pond. Table 3-6: TSF Sediment Pond Volume and Surface Areas Parameter Value Required Contributing Watershed 64 ac Maximum 100 ac Top Width 500 ft Top Length 90 ft Crest Elevation 877 ft Length to Width Ratio 5.6 Minimum 2:1, Maximum 6:1 Pond Slopes 2H:1V Bottom Elevation 865 ft Spillway Invert 870.5 ft Depth to Spillway 5.5 ft Minimum 2 ft Area at Spillway 0.696 ac 0.695 ac Volume at Spillway 3.11 ac ft 2.64 ac-ft Spillway width 50 ft Skimmer Size 8 inch float/6 inch Orifice Nominal Skimmer flow 0.854 cfs/383 gpm Time to Dewater 51 hours Minimum 48 hours Source:SRK,2023a 3.6.2 TSF Collection Pond Seepage and run-off from the TSF will be collected and routed to the Contact Water Management Pond. This pond has been designed to detain the PMF from the filtered tailings area surface as well as the seepage and intercepted groundwater collected by the TSF sump. The TSF collection pond is designed to detain, monitor and release the TSF contact water collected and pumped from the TSF internal sumps, both groundwater seepage collection and stormwater collected in temporary sumps on the surface. Sediment control is not anticipated to be required for these discharges. The TSF Collection Pond is summarized in Table 3-7. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 29 Table 3-7: TSF Collection Ponds Volumes and Surface Areas Parameter Value Top Width 400 ft Top Length 140 ft Crest Elevation 902.5 ft Pond Slopes 2.5H:1V Bottom Elevation 890 ft Spillway Invert 895.5 ft Depth to Spillway 5.5 ft Area at Spillway 1.286 ac Volume at Spillway 34.1 ac-ft Spillway Pipe Diameter 30 inches Skimmer Size 8 inch float/7 inch Orifice or 650 gpm pump with floating inlet Maximum Skimmer flow 1.48 cfs/667 gpm Time to Dewater 42.5 hours Source:SRK,2024 3.7 Surface Water Controls Quantities Quantities to develop the surface water management infrastructure were developed from the PFS- level designs. All quantities include a 15% contingency. These quantities are provided in Table 3-8. Pond areas, channels, and culvert lengths have been estimated from the layout drawings of the surface water controls, while riprap and sand bedding quantities have been estimated from 2x the riprap D5o thickness over the channel section. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report-Kings Mountain Page 30 Table 3-8: Surface Water Management Quantities Low Flow Low Flow Erosion Protection (Riprap or Hydro Turf®) (3) Channel Channel (t) Hydro Turf Reach Surface Bank Full Channel Surface Minimum Riprap Ri y ® Granular prap Filter Filter Designation Perimeter Area Riprap Volume Erosion Volume Thickness (per length) (cy) (ac) Thickness (cy) Material Protection (in) (ft) ft s ft C-PT11a 6.01 71,600 0.2766 C-PT11 b 3.90 22,600 0.1124 2.3 423 Fabric 12,425 C-PT11c 2.85 6,300 0.0363 C-PT12a 3.37 5,400 0.0290 Perimeter Composite Channels C-PT-12b 4.95 47,200 0.2055 C-PT12c 6.11 26,500 0.0858 C-PT12d 7.17 67,500 0.2004 C-PT12e 8.22 36,700 0.1003 5.3 863 Fabric 7,575 C-PT-12f 9.07 34,600 0.0765 3.3 412 Fabric 5,550 NC-AR13a 19.81 52800 0.8348 NC-PAD1 9.49 4200 0.1355 NC-PAD2 9.49 4600 0.1481 NC-PAD3 11.07 4300 0.1181 NC-PAD4 11.07 2200 0.0610 NC-PAD5 9.49 2200 0.0710 NC-PAD6 14.49 8400 0.1949 NC-PAD7 12.91 3100 0.0850 Non Process Infrastructure NC-PAD8 12.91 2700 0.0744 Area Channels NC-SWALE1 32.15 1000 0.0295 NC-SWALE2 27.12 3300 0.1121 NC-SWALE3 32.15 700 0.0207 NC-SWALE4 42.20 17200 0.3788 NC-SWALE5 32.15 10300 0.2974 NC-DS1 17.37 700 0.0179 1.50 43.42 Granular 4 NC-BROW-T14a 12.65 6300 0.1525 NC-BROW-T14b 12.65 7400 0.1800 NC-BROW-T14c 12.65 5600 0.1356 DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 31 Culvert Designation Culvert Diameter Culvert Length (inches) (ft) Culverts Perim-Culvert 18 60 N C-C U LV-TPAD 1 24 440 NC-CULV-TPAD2 18 470 C-CU LV-SPILLWAY 30 325 Source:SRK,2024 (1)Riprap thickness assumed 2 times riprap D50 �2>Granular filter material beneath riprap recommended when bed slope> 10%,filter fabric otherwise �3)Minimum 6 inch granular filter recommended beneath riprap D50 9 inch or greater,4 inch otherwise. DH/M H Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 32 4 Conclusions A site-wide surface water management plan has been prepared and summarized in this document. It can be concluded that: • Three separate conveyance systems will be developed to: o Manage non-contact water produced by the ongoing construction and development of the TSF facility. o Manage the non-contact water produced by the revegetated or resurfaced NPI components associated with the TSF that do not contact mine waste materials. o Manage the contact water produced by placement and management of the filtered tailings produced by the Kings Mountain Lithium project. • Sediment control measures will be in place before any soil disturbance occurs. • The Project requires approximately 6,570 ft of grass lined non-contact water channels in the TSF perimeter corridor, and approximately 7,950 ft of grass lined non-contact channels in the NPI area. • In some portions of the perimeter, notably the Northwest corner, steep grades and high PMF flows have resulted in the calculated riprap D5o requirements exceeding 12". Placing riprap this large is both expensive, and impractical and the design has substituted an alternative erosion protection system of Hydro Turf ® as an engineering equivalent to large diameter riprap lining for the channels. • The Project requires about approximately 2,155 ft of riprap lined non-contact water channels in the TSF perimeter corridor or 27,550 sq ft of Hydro Turf®hardened erosion protection, and less than 50 ft of riprap lined non-contact channels in the NPI Area. • The Project requires one (1) new sediment control pond. • The Project requires one (1) contact water management pond outside the TSF. • The Project requires active management and detention of contact water collected on the top of the TSF. Monitoring of contact water collected from the TSF is required prior to release to the environment. A separate water management system will be required to address stormwater from the TSF. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 33 5 References AWA (2022). Site-Specific Probable Maximum Precipitation Study for Kings Mountain Mining Operations, North Carolina, Applied Weather Associates, September 2021, KM60-EN-RP-9431. FHA(2021). HY-8 culvert analysis software, Federal Highway Administration. Version 7.70.10.0, June 2. 2021 GPI Surveying (2023), lidar survey Kottek, M., J. Grieser, C. Beck, B. Rudolf, and F. Rubel, 2006: World Map of the Koppen-Geiger climate classification updated. Meteorol. Z., 15, 259-263. DOI: 10.1127/0941-2948/2006/0130. NOAA (2023). NOAA Atlas 14 Point Precipitation Frequency Estimates: NC. https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html NRCS, 2004. Part 630 Hydrology National Engineering Handbook, Chapter 10 Estimation of Direct Runoff from Storm Rainfall. United States Department of Agriculture Natural Resources Conservation Service, 210-V1-NEW, July 2004. US Department of Agriculture (USDA) (1986). Urban Hydrology for Small Watersheds. Technical Release 55 (TR-55). US EPA(2016). Storm Water Management Model Reference Manual. Volume I. Hydrology(Revised). EPA/600/R-15/162A I January 2016 US EPA (2017). Storm Water Management Model Reference Manual. Volume II. Hydraulics. EPA/600/R-17/111 USDA NRCS. (2023). Web Soil Survey. https://websoilsurvey.sc.egov.usda.gov/. USDA Forest Service. (2023). Land Areas of the National Forest System. https://www.fs.fed.us/land/staff/lar/LAR2017/FIA data_products/LAR2017/FIA data_products/ SRK (2023a). Water Balance Development Report, SRK Consulting. SRK(2023b). Dam Safety Permit Application for Contact Water Pond, SRK Consulting. Surface Mining Manual (1996). State of North Carolina, Department of Environment, Health and Natural Resources, February 1996. Department of Environment, Health,and Natural Resources. Division of Land Resources. Land Quality Section. February(1996).Surface Mining Manual.A Guide for Permitting, Operation,and Reclamation. State of North Carolina North Carolina Sedimentation Control Commission, North Carolina Department of Environment and Natural Reserves, and the North Carolina Agricultural Extension Services (2013). Erosion and Sediment Control Planning and Design Manual. North Carolina. May 2013. US Army Corps of Engineers (USACE) Hydrologic Engineering Center — Hydrologic Modeling System (HEC-HMS)Version 4.11, July 2023. US Army Corps of Engineers (USACE) Engineering Manual EM1110-2-1601, Hydraulic Design of Flood Control Channels (30 June 1994), Watershed Geo. (2024). Hydro Turf®website (https://watershedgeo.com/products/hydroturf/) DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 34 Disclaimer SRK Consulting (U.S.), Inc. (SRK) has prepared this document for Albemarle Corporation, our client. Any use or decisions by which a third party makes of this document are the responsibility of such third parties. In no circumstance does SRK accept any consequential liability arising from commercial decisions or actions resulting from the use of this report by a third party. The opinions expressed in this document have been based on the information available to SRK at the time of preparation. SRK has exercised all due care in reviewing information supplied by others for use on this project. While SRK has compared key supplied data with expected values, the accuracy of the results and conclusions from the review are entirely reliant on the accuracy and completeness of the supplied data. SRK does not accept responsibility for any errors or omissions in the supplied information, except to the extent that SRK was hired to verify the data. Copyright This report is protected by copyright vested in SRK Consulting (U.S.), Inc. It may not be reproduced or transmitted in any form or by any means whatsoever to any person without the written permission of the copyright holder. DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Page 35 List of Abbreviations The US System for weights and units has been used throughout this report. Tons are reported in short tons of 2,000 lbs. All currency is in U.S. dollars (US$) unless otherwise stated. Abbreviation Unit or Term percent AEP annual exceedance precipitation amsl above mean sea level cfs cubic feet per second FEMA federal emergency management agency FIRM flood insurance rate ma ft feet HDPE high density of eth lene LoM life of mine PCP probable maximum precipitation PFS refeasibilit stud SCS soil conservation service TSF I tailings storage facility USGS I United States Geological Survey DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Appendices Appendices DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Appendices Appendix D-1 : UT to Dixon Branch Stability Assessment DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 UT to Dixon Branch Stability Assessment Albemarle Kings Mountain Lithium Mining Project Cleveland County, North Carolina JANUARY 2024 PREPARED FOR Albemarle Corporation PREPARED BY SWCA Environmental Consultants UT TO DIXON BRANCH STABILITY ASSESSMENT KINGS MOUNTAIN LITHIUM MINING PROJECT CLEVELAND COUNTY, NORTH CAROLINA Prepared for Albemarle Corporation 348 Holiday Inn Drive Kings Mountain, North Carolina 28086 Prepared by SWCA Environmental Consultants 9319 Robert D. Snyder Rd, Suite 436 Charlotte, NC 28223 (980) 305-5750 www.swca.com SWCA Project No. 70316 January 2024 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project CONTENTS 1 Introduction..........................................................................................................................................I 1.1 Background................................................................................................................................... 1 1.2 Objectives.....................................................................................................................................2 2 Stability Assessment.............................................................................................................................2 2.1 Hydrology.....................................................................................................................................2 2.2 Sediment Classification................................................................................................................3 2.2.1 Stream Bed Assessment......................................................................................................3 2.2.2 Stream Bank Assessment....................................................................................................4 2.3 Hydraulic Model...........................................................................................................................5 2.3.1 Methodology.......................................................................................................................5 2.3.2 Results.................................................................................................................................6 3 Conclusion.............................................................................................................................................7 4 References Cited...................................................................................................................................9 5 Glossary...............................................................................................................................................10 Appendices Appendix A. Project Information Appendix B. Hydraulic Model Summary Figures Figure 1. Representitive Photo of UT to Dixon Branch................................................................................2 Figure 2. Representative Photo of Dixon Branch. ........................................................................................3 Figure 3. Observed stream bed material. ......................................................................................................4 Figure4. Observed bedrock control..............................................................................................................5 Figure5. Observed bank erosion. .................................................................................................................6 Tables Table 1. Existing Peak Discharges................................................................................................................3 Table 2. 1-Year Storm Velocity and Shear Stress.........................................................................................6 Table 3. 2-Year Storm Velocity and Shear Stress.........................................................................................6 Table 4. 100-Year Storm Velocity and Shear Stress.....................................................................................7 Table5. Flooding Depth Summary...............................................................................................................7 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project 1 INTRODUCTION On behalf of Albemarle Corporation(Albemarle), SWCA Environmental Consulting and Engineering, Inc. (SWCA)has performed a Stability Assessment for the Unnamed Tributary(UT)to Dixon Branch for the Albemarle Kings Mountain Lithium Mining Project(Project),located in Cleveland County,North Carolina(Appendix A). 1 .1 Background Albemarle is proposing to develop a property known as the Cactus Site as a Tailing Storage Facility (TSF),with stormwater runoff from the TSF to be discharged to the nearby UT to Dixon Branch. UT to Dixon Branch headwaters at the TSF and flows south through a culvert under Interstate 85 (I-85). The confluence with Dixon Branch is approximately 4,560 linear feet downstream of the 1-85 culvert. The Project Reach studied for the purpose of this report extends from the headwaters of the UT to approximately 5,520 linear feet downstream of the confluence with Dixon Branch. The total length of the studied reach is approximately 10,590 linear feet. Figures 1 and 2 below are representative photos of the Project Reach. 41 l� �I 3 . i . Figure 1.Representative photo of UT to Dixon Branch. 1 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project y; Figure 2. Representative photo of Dixon Branch. 1 .2 Objectives This report describes the methodologies,assumptions,and findings of the assessment performed to evaluate the impact of discharging water from the proposed TSF into UT to Dixon Branch. The main objective of this assessment was to evaluate current channel stability and the impacts of the additional discharge, if any,to UT to Dixon Branch. Potential impacts are based on the following major factors: • Changes in flow rate • Impacts to the physical structure of UT to Dixon Branch(increased total suspended solids(TSS) or turbidity from erosion) 2 STABILITY ASSESSMENT 2.1 Hydrology In order to estimate expected flows through the Project Reach and evaluate channel stability, a desktop hydrologic analysis of the watershed was completed. The 1-,2-, and 100-year,24-hour storm events were studied to estimate peak discharges and represent a spectrum of flood events. The watershed(drainage area)for UT to Dixon Branch was delineated using QLl LiDAR data from North Carolina's Spatial Data records. The point of analysis was determined at the confluence of UT to Dixon Branch with Dixon Branch to estimate total runoff experienced at the most downstream point of the UT. A composite curve number was assigned to the delineated area based on land cover derived from the 2021 National Land Cover Database(NLCD)and soil types present according to the Natural Resources Conservation Service(MRCS)Web Soil Survey. The subject watershed was classified mostly as forest 2 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project and developed space encompassing Hydrologic Soil Groups(HSGs) `B', `C,' and `D'. Precipitation data was obtained from NOAA Atlas 14 for Cleveland County,North Carolina. Peak discharges were computed using the NRCS TR-55 method(USDA,NRCS 1986)in the US Army Corp of Engineers (USACE)HEC-HMS Version 4.10 software.A summary of the peak discharges is presented in Table 1. Table 1.Existing Peak Discharges 1-Year Peak Discharge(cfs) 2-Year Peak Discharge(cfs) 100-Year Peak Discharge(cfs) 110.4 164.2 608.8 Note: Discharge values are derived from watershed hydrology and do not include proposed dewatering flow or existing inflow from the proposed TSF. 2.2 Sediment Classification Stream bed and bank material play a significant role in channel hydraulics. Classification of the sediment material and its composition help to estimate erosion rates, sediment supply, and overall channel stability. 2.2.1 Stream Bed Assessment The characterization of sediment size within the channel was conducted based on visual observations as depicted in Figure 3. t _ s 4" 1 r Figure 3. Observed stream bed material. The stream bed material for UT to Dixon Branch can largely be characterized as a boulder and gravel- dominated system,with isolated areas of fine silt/sand and numerous occurrences of bedrock control as can be seen in Figure 4. 3 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project `^�*"�"'tip.,•: - 1 � �� !�'t �, �.. � -�"' Figure 4. Observed bedrock control. 2.2.2 Stream Bank Assessment In addition to classification of stream bed material, an assessment of stream bank condition is important in estimating erosion potential and overall channel stability. Much of the suspended sediment found in streams can be attributed to eroding stream banks. While some bank erosion is expected in a stable stream, changes in watershed hydrology or sediment load due to anthropogenic influences increases the potential for a deviation from naturally occurring erosion. Since flow in UT to Dixon Branch is expected to increase as a result of the proposed development of the TSF, a visual stream bank assessment was performed to determine erodibility potential of the stream banks. Several instances of bank erosion were identified along UT to Dixon Branch(see Figure 5) although they presented as isolated areas of instability and not indicative of a more global issue.Furthermore,the observed areas of bank erosion appeared to be inactive, likely the result of a historic flood event. 4 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project e Figure 5. Observed isolated bank erosion. 2.3 Hydraulic Model A hydraulic model provides quantitative results of channel hydraulics, such as channel velocity, shear stresses, and flood evaluations critical to the evaluation of the channel stability.UT to Dixon Branch was modeled using US Army Corp of Engineers(USACE)HEC-RAS Version 6.1.0 software(USACE 2021). Hydraulic parameters for the stability assessment were computed using the peak discharge estimates and geometry data of the existing channel. 2.3.1 Methodology An existing 1-Dimensional steady-state model of a section of Dixon Branch directly downstream of the confluence with UT to Dixon Branch was obtained from the Federal Emergency Management Agency (FEMA)in December 2023. SWCA extended the existing model upstream to include the entire Project Reach and compare existing and proposed channel hydraulics and the effects of the proposed stormwater discharges from the TSF to the Project Reach and beyond. Based on information received from SRK Consulting in September 2023,the expected stormwater discharge from the TSF is 16.1 cubic feet per second(cfs). Channel and floodplain geometry for UT to Dixon Branch were extracted from QL1 LiDAR data. Manning's n roughness coefficients were determined based on a combination of field reconnaissance and the values used in the existing model. These coefficients were assumed to be 0.035 within the channel, which is representative of a clean winding stream channel, and ranged between 0.04 and 0.10 for low to well vegetated over bank areas. Existing stream structures were built into the model based on field measurements. Steady-state models require both upstream and downstream boundary condition data. Critical depth was assumed for the upstream boundary condition since the water surface elevation is unknown and will vary 5 UT to Dixon Branch Stability Assessment-Kings Mountain Lithium Mining Project based on the proposed TSF outflows. The existing Dixon Branch FEMA model assumed a normal depth of 0.005 was used for the downstream boundary condition. Two scenarios were run and analyzed for UT to Dixon Branch: • Existing conditions • Proposed conditions (with additional flows from the TSF) The existing and proposed conditions used identical geometry and boundary condition data,the only variable being the additional stormwater discharge flow from the proposed TSF. Existing flows were based on watershed hydrology and the estimated peak flows from the 1-year,2-year, and 100-year storm events. It is understood that the proposed point of stormwater discharge has not yet been identified, therefore it was assumed that it is located at the headwaters of UT to Dixon Branch. 2.3.2 Results The results of the hydraulic model were evaluated in terms of channel stability and flooding potential and are summarized in the following sections.Based on the previously described visual assessment of the stream bed material and banks, a threshold of permissible velocity was determined to be 9.0 feet per second(fps)and permissible shear stress 3.0 pounds per square feet(lb/ft2). 2.3.2.1 STABILITY Channel stability was assessed based on permissible velocities and shear stresses on the channel banks during the design storm events,the results of which are shown in the following Tables 2-4. Table 2. 1-Year Storm Velocity and Shear Stress Existing Proposed Percent Existing Shear Proposed Shear Percent Velocity(ft/s) Velocity(ft/s) Increase Stress(lb/ft') Stress Ob/ft2) Increase Minimum 0.47 0.53 12.8% 0.00 0.00 --- Average 5.96 6.10 2.4% 1.22 1.25 2.5% Maximum 9.52 9.40 -1.3% 3.79 3.75 -1.1% Note:All values are for the stream channel across the entire Project Reach from 1-Dimensional Steady-state model. Table 3.2-Year Storm Velocity and Shear Stress Existing Proposed Percent Existing Shear Proposed Shear Percent Velocity(ft/s) Velocity(ft/s) Increase Stress(lb/ft) Stress(lb/ft) Increase Minimum 0.66 0.71 7.6% 0.00 0.01 --- Average 6.56 6.60 0.6% 1.33 1.33 --- Maximum 10.47 10.53 0.6% 5.02 5.07 1.0% Note:All values are for the stream channel across the entire Project Reach from 1-Dimensional Steady-state model. 6 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project Table 4. 100-Year Storm Velocity and Shear Stress Existing Proposed Percent Existing Shear Proposed Shear Percent Velocity(ft/s) Velocity(ft/s) Increase Stress(lb/ft') Stress Ob/ft2) Increase Minimum 0.91 1.21 33.0% 0.02 0.03 50.0% Average 7.92 7.91 -0.1% 1.78 1.77 -0.6% Maximum 16.88 17.26 2.3% 7.19 7.51 4.5% Note:All values are for the stream channel across the entire Project Reach from 1-Dimensional Steady-state model. Several areas were identified along UT to Dixon Branch with velocity and shear stress that exceed permissible limits. These areas presented with a high potential for instability and failure in the existing condition scenario and field assessments revealed notable instances of bank erosion along meander bends and at in-stream structures. Shear stresses exceeding the permissible limits were noted at Station 100+00 and 118+85 which are both meander bend locations (see Appendix A for locations). High velocities were noted downstream each culvert or bridge, likely due to the concentration of flows.While these areas have a higher potential for erosion and instability,the proposed increase in flows to UT to Dixon is minimal and will likely not result in increased instability. Additionally,these areas are localized and likely do not present a global risk to the Project Reach. 2.3.2.2 FLOODING EXTENTS Minimal increases in flooding depth associated with the added discharge are anticipated for UT to Dixon Branch,based on hydraulic model results summarized in Table 5 and Appendix B. The average increases in flood depths do not exceed one foot for any design storm event,and therefore should not result in any adverse impacts as a result of the increase in flows. The greatest increases in flood depth were present only upstream of the I-85 culvert where there was minimal existing runoff. Flooding is not expected to extend beyond the property line or impact adjacent properties. Table 5. Flooding Depth Summary Storm Event Minimum Depth Maximum Depth Average Depth Increase(it) Increase(ft) Increase(ft) 1-Year 0.01 1.69 0.18 2-Year 0.01 1.64 0.19 100-Year 0.00 1.34 0.12 Note:All values are an average of the hydraulic model results for the stream channel across the entire Project Reach. 3 CONCLUSION Based on the existing conditions detailed in this report,the following considerations are recommended: • Institute monitoring efforts for onsite areas exhibiting bank instability. • Conduct stabilization measures for UT to Dixon Branch if monitoring indicates that erosion continues to progress towards instability. 7 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project If proposed discharges into UT to Dixon Branch are implemented with consideration to the recommendations in this report,preservation of the channel's integrity can be maintained while minimizing potential risks associated with bank instability and related hydraulic parameters. However, modifications of the proposed flow regime or restorations may require further analysis. Some modifications that would require analysis to be revised include: • Changes in proposed discharge conditions. • Significant changes in the watershed resulting in increased runoff to the Project Reach. The above modifications may result in the assumptions within this report becoming invalid. The computations within this report will need revisited if any of the above conditions become apparent as the project moves forward. 8 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project 4 REFERENCES CITED Arcement, George J. Jr., Schneider,Verne R. 1989. Guide for Selecting Manning's Roughness Coefficients for Natural Channels and Flood Plains. United States Government Printing Office. U.S. Department of Transportation,Federal Highway Administration. Fischenich, Craig.2001. Stability Thresholds for Stream Restoration Materials. Vicksburg,Mississippi: Ecosystem Management and Restoration Research Program(EMRRP). USAE Research and Development Center,Environmental Laboratory. Rosgen,D. L. 2001.A Practical Method of Computing Streambank Erosion Rate. Pagosa Springs, Colorado: US EPA. SWCA Environmental Consultants (SWCA). 2022a. Wetland and Waterbody Delineation Report for the Albemarle Kings Mountain Lithium Mining Project, Cleveland County, North Carolina. April. SWCA. 2022b.Federally and State-Listed Species Report for the Kings Mountain Lithium Mine, Cleveland County, North Carolina. September. United States Army Corps of Engineers. 2021. HEC-RAS Version 6.1.0. United States Environmental Protection Agency(USEPA). 2022. National Pollutant Discharge Elimination System (NPDES). US EPA. United States Department of Agriculture(USDA),Nation Resources Conservation Service(MRCS). 1986. Urban Hydrology for Small Watersheds: TR-55. USDA. United States Geological Survey(USGS). 2014. Topographic Data Quality Levels (QLs). USGS's 3D Elevation Program. Wolman,M. Gordon. 1954.A method of sampling coarse river-bed material. American Geophysical Union. 9 UT to Dixon Branch Stability Assessment—Kings Mountain Lithium Mining Project 5 GLOSSARY Anthropogenic. Environmental change caused or influenced by people. Bankfull Event. A frequently occurring peak flow event whose stage represents the incipient point of flooding. It is often associated with a return period of 1-2 years,with an average of 1.5 years(Rosgen 1942). Critical Depth. The depth at which the energy of the flow is minimized. Curve Number. A hydrologic parameter based on land use, soil type, and soil moisture to describe stormwater runoff potential for a specified drainage area. Geomorphologic. The study of the origin and evolution of the configuration of landforms. Headwater. A tributary stream of a river close to or forming part of its source. Hydraulics. The branch of science and technology concerned with the conveyance of liquids through pipes and channels, especially as a source of mechanical force or control Hydrology. The branch of science concerned with the properties of the earth's water, and especially its movement in relation to land. Manning's n Roughness Coefficient. Represents an empirically derived resistance coefficient to compute velocity(Rosgen 1942). National Pollutant Discharge Elimination System.A permit program created in 1972 by the Clean Water Act that addresses water pollution by regulating point sources that discharge pollutants to waters of the United States. (USEPA 2022). Permissible Velocities. The highest velocity at which water may be carried safely in a channel. LiDAR. Light Detection and Ranging.A remote sensing system used to collect topographic data. LiDAR images are helpful in areas with heavy vegetation because they depict the terrain and stream features by removing vegetation effects(Rosgen 1942). QLL Quality Level 1. A quality level assigned to LiDAR that has a vertical accuracy of 10 cm, a nominal pulse spacing of less than or equal to 0.35m, and a digital elevation cell size of 0.5m. QL1 is second only to QLO(USGS 2014). Shear Stress. The frictional force per unit area causing flow resistance along the channel boundary. Measured as a depth and slope product multiplied by the specific weight of water(Rosgen 1942). Steady-state model. A HEC-RAS model where discharge remains constant throughout the entire model run. The discharge-stage ratings will represent a kinematic flow. TSS. Total Suspended Sediment. The portion of the total sediment load of rivers that is carried in the water column(Rosgen 1942). Turbidity.The measure of relative clarity of a liquid. 10 APPENDIX A Project Information Vicinity Map Topography Map Soils Map Precipitation Data CIO 'tea . ..- Archdale ..ate `' I � � •�•!} t d Ir •.4 - } IL oUrid. - ��• - �. %. �v -i � •T A, i. r .�;Q � �a 01 . Rd- !� �Caveny S ;111111km �- IV i4i ti� - „CCU r '"r. •�;:�.y'. .Y*' ,�\\ ClevelandEO UT TO DIXON BRANCH STABILITY ASSESSMENT FSSIWCA County, i —216� ' e 29 e 0 0 � e n v ApB 0 McC2 0 ChA MnB GrD 0 PeD HhB UdC HtC 0 <all other values> MaB2 Delineated Area MbB2 Backgmund: USGS Web Soil Survey Scale: 1:15,000 CreateO By: M.Anpl.Angel UT TO DIXON BRANCH STABILITY ASSESSMENT Datewod,ced a Allen SWCA Prq—No.: 70316 SWCADate Produced: December 20,2023 Cleveland County, North Carolina GCS WGS 1984 ENVIRONMENTAL CONSULTANTS 0 1,000 2,000 SOILS MAP an Kilome ers 0 032 0.63 -- -- 40 /f tv Y' (:vs II ill �r aP 0 T S$P moll.- x 'Z 6 x ' 0 DelineatedArea Backgrou,d: 2018 ESRI Imagery Scale: 1:12,000 Created By: nm,al UT TO DIXON BRANCH STABILITY ASSESSMENT Daewe Alle" SWCA Pro—No.: 20316 SWCADatte Produced: December 20,2023 Cleveland County, North Carolina NAD 19832011 StatePlaue North Carolina FIPS 3200 Ft US ENVIRONMENTAL CONSULTANTS 0 1,000 2,000 TOPOGRAPHY MAP Feet Kilometers 0 0,25 0.5 i•26pO r� 88 S 0 il6°o0 _ o0 00 --400 i0000 9600 9350 9j,0 9000 o �o 8 780o a°o �6 00 s �qoo 0 Dixon Branch CL ,l0,50 o UT to Dixon CL 6616 FEMA XS SWCA XS = 6-20 Elevation Contours bo" Delineated Area Backgrou,d: 2018 ESRI Imagery Scale: 1:12,000 Created By: M.Angel UT TO DIXON BRANCH STABILITY ASSESSMENT Date wed oduce Allen SWCA Project No.: 20316 SWCADate Produced: January 09,2029 Cleveland County, North Carolina NAD 19832011 StatePlane North Carolina FIPS 3200 Ft US ENVIRONMENTAL CONSULTANTS 0 1,000 2,000 HYDRAULIC MODEL MAP Fee` Kilometers 0 0,25 0.5 NOAA Atlas 14,Volume 2,Version 3 Location name: Kings Mountain, North Carolina, • / USA* Latitude: 35.1884*, Longitude: -81.4052* Elevation:908 ft** source:ESRI Maps source:USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley NOAA,National Weather Service,Silver Spring,Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval(years) Duration� 2 � 10 25 50 100 200 500 1000 5-min 0.408 0.483 0.566 0.629 70 0. 7 0.763 0.818 0.872 0.940 0.993 (0.374-0.447) (0.443-0.528) (0.517-0.619) (0.573-0.687) (0.641-0.771) (0.688-0.833) (0.735-0.894) (0.778-0.954) (0.830-1.03) (0.869-1.09) 10-min 0.652 0.772 0.906 1.01 F 1.13 1.22 1.30 1.38 1.49 1.56 (0.597-0.713) (0.708-0.845) (0.828-0.991) (0.916-1.10) 1 (1.02-1.23) 1 (1.17-1.42) 11 (1.23-1.51) (1.31-1.63) (1.37-1.72) 15-min 0.815 0.971 1.15 1.27 1.43 1.54 1.64 1.74 1.87 1.96 (0.746-0.892) (0.890-1.06) 1 (1.05-1.25) 1 (1.29-1.56) 1 (1.39-1.68) 1 (1.48-1.80) 11 (1.56-1.91) (1.65-2.05) (1.72-2.16) 30-min 1.12 1.34 1.63 1.84 2.11 2.32 2.52 2.72 2.98 3.18 (1.02-1.22) 1 (1.23-1.47) 1 (1.49-1.78) 1 (1.68-2.01) 1 (1.92-2.31) 1 (2.09-2.53) 1 (2.26-2.75) 11 (2.42-2.97) (2.63-3.26) (2.78-3.50) 60-min 1.39 1.68 2.09 2.40 2.82 3.14 3.47 3.81 4.27 4.64 (1.28-1.52) 1 (1.54-1.84) 1 (1.91-2.28) 1 (2.19-2.62) (2.55-3.07) (2.83-3.43) 1 (3.12-3.79) 11 (3.40-4.16) (3.77-4.68) (4.06-5.11) 2-hr 1.62 1.96 2.44 2.83 3.36 3.79 4.24 4.72 5.40 5.97 ) (1.48-1.77) (1.79-2.15) (2.24-2.68) (2.58-3.09) (3.05-3.67) (3.42-4.14) (3.80-4.63) 11 (4.21-5.17) (4.76-5.93) (5.21-6.58 L3-hr 1.72 2.08 2.60 3.03 3.634.68 5.27 6.12 6.85 (1.57-1.90) (1.90-2.29) (2.38-2.87) (2.75-3.33) (3.28-3.99) (3.72-4.55) (4.17-5.14) (4.65-5.80) (5.33-6.76) (5.90-7.58) 6-hr 2.10 2.52 3.15 3.67 4.41 5.04 5.71 6.44 7.52 8.43 (1.93-2.30) 1 (2.32-2.77) (2.89-3.46) (3.35-4.02) (4.00-4.82) (4.54-5.50) (5.10-6.23) (5.70-7.04) (6.54-8.23) (7.25-9.26) 12-hr 2.52 3.05 3.82 4.44 5.36 6.12 6.95 7.85 ) ( 9.19 10.3 ) (2.32-2.76) (2.80-3.34) (3.50-4.17) (4.06-4.85) (4.86-5.83) (5.51-6.66) (6.20-7.55) (6.93-8.53 7.98-10.0) (8.86-11.3 24-hr 3.03 3.66 4.60 5.34 6.37 7.19 8.04 8.93 10.2 F 11.2 (2.81-3.27) (3.40-3.96) (4.27-4.97) (4.94-5.77) (5.87-6.86) (6.61-7.74) (7.36-8.67) (8.14-9.62) (9.21-11.0) (10.1-12.0) 2-day 3.59 4.33 5.41 6.26 7.43 T 8.37 9.34 10.3 11.7 12.9 (3.33-3.88) (4.02-4.68) (5.02-5.84) 1 (5.80-6.75) (6.86-8.00) (7.70-9.01) 1 (8.55-10.1) 11 (9.44-11.2) (10.6-12.7) (11.6-13.9) 3-day 3.81 4.58 5.69 6.57 7.77 8.73 9.71 10.7 12.1 13.3 (3.55-4.10) (4.26-4.94) (5.28-6.12) (6.09-7.07) (7.17-8.35) (8.04-9.38) (8.92-10.4) (9.82-11.5) (11.1-13.1) (12.0-14.3) 4-day 4.04 4.84 5.98 6.88 8.10 9.08 10.1 11.1 IF 12.5 13.7 (3.76-4.33) (4.51-5.20) (5.56-6.42) (6.38-7.38) (7.49-8.69) (8.38-9.74) (9.28-10.8) 1 (10.2-11.9) 1 (11.5-13.5) (12.4-14.7) 7-day 4.68 5.59 6.81 7.78 9.12 F 10.2 F 11.3 12.4 13.9 15.2 (4.39-4.99) (5.24-5.96) (6.38-7.25) (7.28-8.29) (8.50-9.71) 1 (9.47-10.8) 1 (10.5-12.0 1 (11.5-13.2) (12.8-14.9) (13.9-16.2) Eio7ay- 5.32 6.33 7.62 8.62 9.98 11.0 12.1 13.2 14.7 15.9 (5.02-5.66) (5.97-6.74) (7.17-8.10) (8.10-9.16) (9.36-10.6) (10.3-11.7) (11.3-12.9) 1 (12.3-14.1) (13.6-15.7) (14.7-16.9) 20-day 7.10 8.38 9.89 11 12.7 14.0 15.2 16.5 18.3 19.6 (6.72-7.49) (7.94-8.84) (9.36-10.4) FL10.5--111.7) (12.0-13.4) (13.1-14.7) 1 (14.3-16.1) 1 (15.4-17.5) (17.0-19.3) (18.2-20.8) 30-day 8.67 10.2 11.9 13.1 14.8 16.2 17.4 18.7 20.5 21.8 (8.25-9.10) (9.71-10.7) (11.3-12.5) (12.5-13.8) (14.1-15.6) i (15.3-17.0) (16.5-18.3) (17.6-19.7) (19.2-21.6) (20.4-23.0) 45-day 10.9 12.8 14.6 7 16.0 F 17.9 19.2 20.6 21.9 23.7 25.0 (10.5-11.4) (12.2-13.4) (14.0-15.3) (15.3-16.7) (17.0-18.6) (18.3-20.1) 11 (19.6-21.5) 11 (20.8-22.9) (22.4-24.8) (23.5-26.2) 60-day 13.0 15.2 17.2 18.7 20.7 22.2 23.6 25.0 26.8 28.2 (12.5-13.6) (14.6-15.8) E(16.5-17.9) (17.9-19.4) (19.8-21.5) (21.2-23.1) (22.5-24.6) (23.8-26.0) (25.5-28.0) (26.7-29.5) 1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates (for a given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values. Please refer to NOAAAtlas 14 document for more information. Back to Top PF graphical UT to Dixon Branch Stability Assessment Rainfall Hyetographs 1 year 24-hr Precip= 3.03 2 year 24-hr Precip= 3.66 100 year 24-hr Precip= 8.04 Cumulative Cumulative Cumulative T(hrs) Precip.(in) Precip.(in) T(hrs) Precip.(in) Precip.(in) T(hrs) Precip.(in) Precip.(in) 0 0.000 0.000 0 0.000 0.000 0 0.000 0.000 1 0.033 0.033 1 0.040 0.040 1 0.088 0.088 2 0.067 0.033 2 0.081 0.040 2 0.177 0.088 3 0.103 0.036 3 0.124 0.044 3 0.273 0.096 4 0.145 0.042 4 0.176 0.051 4 0.386 0.113 5 0.191 0.045 5 0.231 0.055 5 0.507 0.121 6 0.242 0.052 6 0.293 0.062 6 0.643 0.137 7 0.297 0.055 7 0.359 0.066 7 0.788 0.145 8 0.364 0.067 8 0.439 0.081 8 0.965 0.177 9 0.445 0.082 9 0.538 0.099 9 1.182 0.217 10 0.548 0.103 10 0.662 0.124 10 1.455 0.273 11 0.712 0.164 11 0.860 0.198 11 1.889 0.434 12 2.227 1.515 12 2.690 1.830 12 5.909 4.020 13 2.339 0.112 13 2.826 0.135 13 6.207 0.297 14 2.485 0.145 14 3.001 0.176 14 6.593 0.386 15 2.588 0.103 15 3.126 0.124 15 6.866 0.273 16 2.666 0.079 16 3.221 0.095 16 7.075 0.209 17 2.736 0.070 17 3.305 0.084 17 7.260 0.185 18 2.794 0.058 18 3.375 0.070 18 7.413 0.153 19 2.842 0.048 19 3.433 0.059 19 7.542 0.129 20 2.885 0.042 20 3.484 0.051 20 7.654 0.113 21 2.921 0.036 21 3.528 0.044 21 7.751 0.096 22 2.957 0.036 22 3.572 0.044 22 7.847 0.096 23 2.994 0.036 23 3.616 0.044 23 7.944 0.096 24 3.030 0.036 24 3.660 0.044 24 8.040 0.096 1-yr 24-hr Storm Event 2-yr 24-hr Storm Event 100-yr 24-hr Storm Event 1.600 3.500 2.000 4.000 4.500 9.000 1.400 3.000 1.800 3.500 4.000 8.000 1.200 1.600 3.500 7.000 1.000 2.500 2.500 3.000 1.400 3.000 6.000 2.000 1.200 1 2.500 5.000 0.800 1.000 2.000 1.500 2.000 4.000 0.600 0.800 - 1.500 1.000 0.600 1.500 3.000 0.400 1.000 1.000 2.000 0.400 0.200 0.500 0.500 0.200 0.500 1.000 0.000 ■■■�11�I ��11��■.... 0.000 0.000 ■■■111� III111I■.... 0.000 0.000 ■■■■11�I 11....... 0.000 1 3 5 7 9 11 13 15 17 19 21 23 25 1 3 5 7 9 11 13 15 17 19 21 23 25 1 3 5 7 9 11 13 15 17 19 21 23 25 APPENDIX B HYDRAULIC MODEL SUMMARY Output Tables Reach Profile Station Cross Sections HEC-RAS Plan:Ex River:UTtoDixon Reach:UTtoDixon Reach River Sta Profile Q Total Min Ch El W.S.Elev Val Chnl Flow Area Top Width Shear Chan Crit Depth Max Chl Dpth (cfs) (ft) (ft) (ft/s) (sq ft) (ft) (lb/sq ft) (ft) (ft) UTtoDixon 13275 1-year 0.15 853.91 854.02 0.82 0.18 10.08 0.09 0.11 0.11 UTtoDixon 13275 2-year 0.15 853.91 854.02 0.82 0.18 10.08 0.09 0.11 0.11 UTtoDixon 13275 100-year 0.15 853.91 854.02 0.82 0.18 10.08 0.09 0.11 0.11 UTtoDixon 13209 1-year 0.15 850.63 851.08 0.06 2.62 6.99 0.00 0.03 0.45 UTtoDixon 13209 2-year 0.15 850.63 851.08 0.06 2.62 6.99 0.00 0.03 0.45 UTtoDixon 13209 100-year 0.15 850.63 851.08 0.06 2.62 6.99 0.00 0.03 0.45 UTtoDixon 13159 Culvert UTtoDixon 12929 1-year 5.50 845.00 845.19 2.45 2.25 11.94 0.36 0.19 0.19 UTtoDixon 12929 2-year 8.20 845.00 845.25 2.78 2.94 12.09 0.43 0.25 0.25 UTtoDixon 12929 100-year 30.50 845.00 846.79 1.18 31.64 24.74 0.04 0.59 1.79 UTtoDixon 12886 1-year 5.50 843.00 843.90 0.98 5.59 7.19 0.04 0.32 0.90 UTtoDixon 12886 2-year 8.20 843.00 844.14 1.11 7.92 11.89 0.04 0.42 1.14 UTtoDixon 12886 100-year 30.50 843.00 846.79 0.91 47.60 30.01 0.02 0.95 3.79 UTtoDixon 12876 Culvert UTtoDixon 12835 1-year 110.00 840.00 841.89 5.68 21.61 15.12 0.94 1.63 1.89 UTtoDixon 12835 2-year 164.00 840.00 842.26 6.90 27.11 19.29 1.31 2.07 2.26 UTtoDixon 12835 100-year 609.00 840.00 844.72 10.77 71.81 83.99 2.47 4.72 4.72 UTtoDixon 12775 1-year 110.00 839.00 840.89 7.20 18.63 13.88 1.54 1.89 1.89 UTtoDixon 12775 2-year 164.00 839.00 841.47 7.65 29.90 21.06 1.57 2.47 2.47 UTtoDixon 12775 100-year 609.00 839.00 843.47 9.54 118.91 66.11 2.00 4.47 4.47 UTtoDixon 12600 1-year 110.00 831.00 832.64 6.32 24.05 24.59 1.23 1.64 1.64 UTtoDixon 12600 2-year 164.00 831.00 832.92 7.56 31.16 25.24 1.67 1.92 1.92 UTtoDixon 12600 100-year 609.00 831.00 834.81 10.25 113.75 48.61 2.41 3.81 3.81 UTtoDixon 12200 1-year 110.00 821.19 823.90 7.57 16.01 11.02 1.71 2.71 2.71 UTtoDixon 12200 2-year 164.00 821.19 824.54 7.69 25.75 16.56 1.60 3.35 3.35 UTtoDixon 12200 100-year 609.00 821.19 826.69 8.33 149.61 126.50 1.53 4.80 5.50 UTtoDixon 11885 1-year 110.00 816.00 817.64 6.48 18.81 16.24 1.30 1.64 1.64 UTtoDixon 11885 2-year 164.00 816.00 817.95 7.71 24.04 17.19 1.73 1.95 1.95 UTtoDixon 11885 100-year 609.00 816.00 818.92 16.88 44.37 22.16 7.19 2.92 2.92 UTtoDixon 11600 1-year 110.00 810.00 811.54 5.61 30.33 59.13 1.16 1.54 1.54 UTtoDixon 11600 2-year 164.00 810.00 811.67 6.26 38.34 59.40 1.38 1.67 1.67 UTtoDixon 11600 100-year 609.00 810.00 812.54 8.40 92.71 65.31 2.06 2.54 2.54 UTtoDixon 11200 1-year 110.00 783.00 784.64 6.74 18.87 15.96 1.40 1.64 1.64 UTtoDixon 11200 2-year 164.00 783.00 784.98 8.08 24.40 17.00 1.89 1.98 1.98 UTtoDixon 11200 100-year 609.00 783.00 787.56 11.14 87.03 30.09 2.68 4.56 4.56 UTtoDixon 11000 1-year 110.00 774.00 775.37 6.07 20.24 21.15 1.20 1.37 1.37 UTtoDixon 11000 2-year 164.00 774.00 775.72 6.97 27.62 21.87 1.46 1.72 1.72 UTtoDixon 11000 100-year 609.00 774.00 777.76 10.29 85.87 33.60 2.42 3.76 3.76 UTtoDixon 10600 1-year 110.00 759.00 760.56 6.39 22.78 23.25 1.28 1.56 1.56 UTtoDixon 10600 2-year 164.00 759.00 760.90 7.51 30.63 24.60 1.65 1.90 1.90 UTtoDixon 10600 100-year 609.00 759.00 763.22 10.14 121.20 54.17 2.29 4.22 4.22 UTtoDixon 10200 1-year 110.00 747.00 748.35 6.21 18.08 16.09 1.26 1.35 1.35 UTtoDixon 10200 2-year 164.00 747.00 748.71 7.06 24.10 16.80 1.50 1.71 1.71 UTtoDixon 10200 100-year 609.00 747.00 750.83 10.40 68.80 24.83 2.46 3.83 3.83 UTtoDixon 10000 1-year 110.00 742.00 743.70 6.48 24.38 23.85 1.28 1.70 1.70 UTtoDixon 10000 2-year 164.00 742.00 743.97 7.93 30.73 24.48 1.82 1.97 1.97 UTtoDixon 10000 100-year 609.00 742.00 745.86 11.95 92.29 37.78 3.28 3.86 3.86 UTtoDixon 9600 1-year 110.00 736.00 740.29 1.76 91.47 37.93 0.07 4.29 UTtoDixon 9600 2-year 164.00 736.00 740.76 2.28 110.04 41.55 0.11 4.76 UTtoDixon 9600 100-year 609.00 736.00 742.95 3.86 318.12 119.74 0.28 6.95 UTtoDixon 9350 1-year 110.00 733.00 740.31 0.57 425.50 169.22 0.01 7.31 UTtoDixon 9350 2-year 164.00 733.00 740.79 0.72 510.23 180.84 0.01 7.79 UTtoDixon 9350 100-year 609.00 733.00 743.00 1.44 969.69 223.82 0.03 10.00 UTtoDixon 9120 1-year 110.00 731.00 740.31 0.47 301.46 223.19 0.00 1.28 9.31 UTtoDixon 9120 2-year 164.00 731.00 740.79 0.66 319.65 225.14 0.01 1.60 9.79 HEC-RAS Plan:Ex River:UTtoDixon Reach:UTtoDixon(Continued) Reach River Sta Profile Q Total Min Ch El W.S.Elev Val Chnl Flow Area Top Width Shear Chan Crit Depth Max Chl Dpth (cfs) (ft) (ft) (ft/s) (sq ft) (ft) (lb/sq ft) (ft) (ft) UTtoDixon 9120 100-year 609.00 731.00 742.94 1.95 401.14 242.14 0.06 3.48 11.94 UTtoDixon 9105 Culvert UTtoDixon 9075 1-year 110.00 730.00 731.61 6.32 17.74 15.27 1.96 1.61 1.61 UTtoDixon 9075 2-year 164.00 730.00 732.02 7.07 24.46 18.06 2.23 2.02 2.02 UTtoDixon 9075 100-year 609.00 730.00 734.13 9.02 90.24 110.81 2.77 4.13 4.13 UTtoDixon 9000 1-year 110.00 727.57 729.95 5.19 21.21 12.85 0.81 1.97 2.38 UTtoDixon 9000 2-year 164.00 727.57 730.34 6.26 26.55 14.16 1.10 2.42 2.77 UTtoDixon 9000 100-year 609.00 727.57 732.77 7.32 148.00 119.74 1.16 5.20 5.20 UTtoDixon 8600 1-year 110.00 723.00 724.92 6.47 17.00 13.05 1.36 1.92 1.92 UTtoDixon 8600 2-year 164.00 723.00 725.34 7.23 23.42 16.28 1.56 2.34 2.34 UTtoDixon 8600 100-year 609.00 723.00 727.63 10.75 69.88 25.35 2.59 4.63 4.63 UTtoDixon 8200 1-year 804.00 717.00 722.73 4.02 283.06 88.16 0.33 5.73 UTtoDixon 8200 2-year 1399.00 717.00 724.46 4.37 441.89 95.98 0.35 7.46 UTtoDixon 8200 100-year 1708.00 717.00 725.66 4.07 612.25 181.92 0.29 8.66 UTtoDixon 7800 1-year 804.00 716.00 721.02 8.57 122.67 45.81 1.61 5.02 UTtoDixon 7800 2-year 1399.00 716.00 723.09 8.47 223.07 51.50 1.37 7.09 UTtoDixon 7800 100-year 1708.00 716.00 724.02 10.06 273.61 87.63 1.85 6.29 8.02 UTtoDixon 7600 1-year 804.00 714.00 720.83 5.40 217.27 49.29 0.56 6.83 UTtoDixon 7600 2-year 1399.00 714.00 722.74 6.94 322.33 61.70 0.85 8.74 UTtoDixon 7600 100-year 1708.00 714.00 723.66 7.46 387.36 75.98 0.95 9.66 UTtoDixon 7400 1-year 804.00 713.00 720.33 6.33 180.56 39.54 0.76 7.33 UTtoDixon 7400 2-year 1399.00 713.00 721.99 8.46 251.58 45.97 1.27 8.99 UTtoDixon 7400 100-year 1708.00 713.00 722.81 9.26 292.19 51.25 1.47 9.81 UTtoDixon 7150 1-year 804.00 714.00 719.60 7.03 158.59 46.52 0.99 4.26 5.60 UTtoDixon 7150 2-year 1399.00 714.00 721.31 8.48 247.17 57.32 1.32 5.66 7.31 UTtoDixon 7150 100-year 1708.00 714.00 722.01 9.56 288.57 82.14 1.62 6.32 8.01 UTtoDixon 7125 Bridge UTtoDixon 7050 1-year 804.00 712.10 718.66 5.21 219.03 57.36 0.53 4.21 6.56 UTtoDixon 7050 2-year 1399.00 712.10 720.27 6.68 322.79 92.61 0.81 5.54 8.17 UTtoDixon 7050 100-year 1708.00 712.10 720.98 7.02 376.56 102.70 0.86 6.22 8.88 UTtoDixon 6950 1-year 804.00 712.00 718.03 7.42 147.33 45.93 1.12 6.03 UTtoDixon 6950 2-year 1399.00 712.00 719.54 9.00 256.14 120.15 1.51 6.34 7.54 UTtoDixon 6950 100-year 1708.00 712.00 720.20 9.60 342.67 150.35 1.67 6.87 8.20 UTtoDixon 6616 1-year 804.00 710.76 716.67 6.62 167.39 53.53 1.78 5.91 UTtoDixon 6616 2-year 1399.00 710.76 717.76 8.92 232.74 64.54 3.04 7.00 UTtoDixon 6616 100-year 1708.00 710.76 718.25 9.80 265.42 68.65 3.58 7.49 UTtoDixon 6209 1-year 804.00 707.33 713.76 7.55 179.93 106.54 2.45 5.72 6.43 UTtoDixon 6209 2-year 1399.00 707.33 717.36 3.83 745.11 298.47 0.54 10.03 UTtoDixon 6209 100-year 1708.00 707.33 718.17 3.47 1001.96 336.36 0.43 10.84 UTtoDixon 6011 1-year 804.00 705.77 711.11 9.52 104.99 37.81 3.79 4.88 5.34 UTtoDixon 6011 2-year 1399.00 705.77 717.15 4.02 925.72 396.54 0.52 11.38 UTtoDixon 6011 100-year 1708.00 705.77 718.04 3.41 1288.35 413.39 0.37 12.27 UTtoDixon 5656 1-year 804.00 702.55 710.97 3.61 363.49 67.44 0.48 8.42 UTtoDixon 5656 2-year 1399.00 702.55 717.01 2.88 817.74 82.97 0.26 14.46 UTtoDixon 5656 100-year 1708.00 702.55 717.87 3.26 889.65 85.50 0.32 15.32 UTtoDixon 5602 1-year 804.00 701.00 710.43 5.81 138.50 50.57 1.24 4.67 9.43 UTtoDixon 5602 2-year 1399.00 701.00 716.41 6.13 228.11 77.76 1.17 6.67 15.41 UTtoDixon 5602 100-year 1708.00 701.00 717.03 7.19 237.48 79.11 1.58 7.60 16.03 UTtoDixon 5521 Culvert UTtoDixon 5418 1-year 804.00 696.00 700.61 8.74 118.66 64.89 3.72 4.61 4.61 UTtoDixon 5418 2-year 1399.00 696.00 701.49 10.47 170.87 69.77 5.02 5.49 5.49 UTtoDixon 5418 100-year 1708.00 696.00 701.87 11.19 193.36 72.49 5.59 5.87 5.87 UTtoDixon 5255 1-year 804.00 693.04 698.24 8.56 122.36 66.28 1.59 5.20 5.20 UTtoDixon 5255 2-year 1399.00 693.04 699.33 9.50 218.11 105.33 1.82 6.29 6.29 HEC-RAS Plan:Ex River:UTtoDixon Reach:UTtoDixon(Continued) Reach River Sta Profile Q Total Min Ch El W.S.Elev Val Chnl Flow Area Top Width Shear Chan Crit Depth Max Chl Dpth (cfs) (ft) (ft) (ft/s) (sq ft) (ft) (lb/sq ft) (ft) (ft) UTtoDixon 5255 100-year 1708.00 693.04 699.66 10.12 254.09 112.51 2.03 6.62 6.62 UTtoDixon 4732 1-year 804.00 688.41 692.97 9.14 96.51 52.07 1.97 4.38 4.56 UTtoDixon 4732 2-year 1399.00 688.41 694.31 9.88 190.06 74.96 2.06 5.90 5.90 UTtoDixon 4732 100-year 1708.00 688.41 694.86 10.13 231.68 76.61 2.09 6.45 6.45 UTtoDixon 4414 1-year 804.00 686.37 691.29 6.91 125.31 47.79 1.07 4.92 UTtoDixon 4414 2-year 1399.00 686.37 692.95 7.10 248.02 118.90 1.00 6.58 UTtoDixon 4414 100-year 1708.00 686.37 692.87 8.89 238.71 97.99 1.58 6.19 6.50 UTtoDixon 4042 1-year 804.00 684.25 689.69 7.06 126.43 41.24 1.06 5.44 UTtoDixon 4042 2-year 1399.00 684.25 690.41 10.23 159.25 49.43 2.12 5.79 6.16 UTtoDixon 4042 100-year 1708.00 684.25 691.80 7.66 430.06 319.02 1.10 7.55 7.55 UTtoDixon 3616 1-year 804.00 683.12 688.24 6.88 272.24 297.15 1.02 5.12 5.12 UTtoDixon 3616 2-year 1399.00 683.12 688.65 8.24 402.36 325.30 1.42 5.53 5.53 UTtoDixon 3616 100-year 1708.00 683.12 688.81 8.71 457.31 329.69 1.57 5.69 5.69 UTtoDixon 3129 1-year 804.00 680.27 685.03 8.17 114.85 95.38 1.51 4.31 4.76 UTtoDixon 3129 2-year 1399.00 680.27 686.24 7.13 393.78 378.48 1.05 5.97 5.97 UTtoDixon 3129 100-year 1708.00 680.27 686.45 7.34 473.72 384.11 1.10 6.18 6.18 UTtoDixon 2685 1-year 804.00 677.41 682.90 4.88 173.79 60.01 1.10 4.19 5.49 UTtoDixon 2685 2-year 1399.00 677.41 684.02 5.80 355.19 264.12 1.43 5.11 6.61 UTtoDixon 2685 100-year 1708.00 677.41 684.56 6.23 520.26 342.92 1.59 5.51 7.15 HEC-RAS Plan:Pr River:UTtoDixon Reach:UTtoDixon Reach River Sta Profile Q Total Min Ch El W.S.Elev Val Chnl Flow Area Top Width Shear Chan Crit Depth Max Chl Dpth (cfs) (ft) (ft) (ft/s) (sq ft) (ft) (lb/sq ft) (ft) (ft) UTtoDixon 13275 1-year 16.25 853.91 854.42 3.58 4.54 11.51 0.61 0.51 0.51 UTtoDixon 13275 2-year 16.25 853.91 854.42 3.58 4.54 11.51 0.61 0.51 0.51 UTtoDixon 13275 100-year 16.25 853.91 854.42 3.58 4.54 11.51 0.61 0.51 0.51 UTtoDixon 13209 1-year 16.25 850.63 852.67 1.17 16.12 9.85 0.04 0.63 2.04 UTtoDixon 13209 2-year 16.25 850.63 852.67 1.17 16.12 9.85 0.04 0.63 2.04 UTtoDixon 13209 100-year 16.25 850.63 852.42 1.35 13.67 9.50 0.05 0.63 1.79 UTtoDixon 13159 Culvert UTtoDixon 12929 1-year 21.60 845.00 845.50 3.59 6.01 12.73 0.58 0.47 0.50 UTtoDixon 12929 2-year 24.30 845.00 845.74 2.65 9.17 13.31 0.28 0.51 0.74 UTtoDixon 12929 100-year 46.60 845.00 847.26 1.38 45.38 33.63 0.05 0.77 2.26 UTtoDixon 12886 1-year 21.60 843.00 845.59 1.05 28.02 19.00 0.03 0.76 2.59 UTtoDixon 12886 2-year 24.30 843.00 845.78 1.08 31.07 19.42 0.03 0.82 2.78 UTtoDixon 12886 100-year 46.60 843.00 847.26 1.21 55.13 47.79 0.03 1.26 4.26 UTtoDixon 12876 Culvert UTtoDixon 12835 1-year 126.10 840.00 842.09 5.81 24.55 18.90 0.95 1.77 2.09 UTtoDixon 12835 2-year 180.10 840.00 842.36 7.22 28.61 19.50 1.41 2.19 2.36 UTtoDixon 12835 100-year 625.10 840.00 844.77 10.87 73.10 84.15 2.51 4.77 4.77 UTtoDixon 12775 1-year 126.10 839.00 840.98 7.80 19.91 14.06 1.77 1.98 1.98 UTtoDixon 12775 2-year 180.10 839.00 841.58 7.89 32.31 21.28 1.65 2.58 2.58 UTtoDixon 12775 100-year 625.10 839.00 843.50 9.62 121.31 66.25 2.02 4.50 4.50 UTtoDixon 12600 1-year 126.10 831.00 832.75 6.62 26.76 24.80 1.32 1.75 1.75 UTtoDixon 12600 2-year 180.10 831.00 832.98 8.01 32.49 25.42 1.85 1.98 1.98 UTtoDixon 12600 100-year 625.10 831.00 834.82 10.48 114.17 48.63 2.51 3.82 3.82 UTtoDixon 12200 1-year 126.10 821.19 824.25 7.06 21.10 15.99 1.41 3.06 3.06 UTtoDixon 12200 2-year 180.10 821.19 824.68 7.77 28.21 16.87 1.61 3.49 3.49 UTtoDixon 12200 100-year 625.10 821.19 826.75 8.08 157.26 126.65 1.43 4.63 5.56 UTtoDixon 11885 1-year 126.10 816.00 817.76 6.75 20.84 16.47 1.38 1.76 1.76 UTtoDixon 11885 2-year 180.10 816.00 818.22 7.27 29.36 20.80 1.47 2.22 2.22 UTtoDixon 11885 100-year 625.10 816.00 818.93 17.26 44.55 22.18 7.51 2.93 2.93 UTtoDixon 11600 1-year 126.10 810.00 811.58 5.79 33.00 59.22 1.21 1.58 1.58 UTtoDixon 11600 2-year 180.10 810.00 811.70 6.50 40.11 59.46 1.48 1.70 1.70 UTtoDixon 11600 100-year 625.10 810.00 812.56 8.46 94.30 65.36 2.08 2.56 2.56 UTtoDixon 11200 1-year 126.10 783.00 784.77 7.05 20.99 16.18 1.50 1.77 1.77 UTtoDixon 11200 2-year 180.10 783.00 785.23 7.74 29.31 20.02 1.66 2.23 2.23 UTtoDixon 11200 100-year 625.10 783.00 787.61 11.28 88.56 30.18 2.73 4.61 4.61 UTtoDixon 11000 1-year 126.10 774.00 775.48 6.36 22.56 21.38 1.28 1.48 1.48 UTtoDixon 11000 2-year 180.10 774.00 775.81 7.18 29.73 22.16 1.52 1.81 1.81 UTtoDixon 11000 100-year 625.10 774.00 777.80 10.44 87.13 33.71 2.48 3.80 3.80 UTtoDixon 10600 1-year 126.10 759.00 760.68 6.70 25.47 23.50 1.37 1.68 1.68 UTtoDixon 10600 2-year 180.10 759.00 760.97 7.86 32.59 24.94 1.78 1.97 1.97 UTtoDixon 10600 100-year 625.10 759.00 763.29 10.13 125.22 54.34 2.28 4.29 4.29 UTtoDixon 10200 1-year 126.10 747.00 748.47 6.48 19.99 16.32 1.33 1.47 1.47 UTtoDixon 10200 2-year 180.10 747.00 748.82 7.27 25.83 17.02 1.56 1.82 1.82 UTtoDixon 10200 100-year 625.10 747.00 750.81 10.76 68.16 24.78 2.64 3.81 3.81 UTtoDixon 10000 1-year 126.10 742.00 743.82 6.79 27.12 24.06 1.37 1.82 1.82 UTtoDixon 10000 2-year 180.10 742.00 744.23 7.44 38.15 29.13 1.54 2.23 2.23 UTtoDixon 10000 100-year 625.10 742.00 745.89 12.13 93.44 37.91 3.37 3.89 3.89 UTtoDixon 9600 1-year 126.10 736.00 740.48 1.90 98.61 38.98 0.08 4.48 UTtoDixon 9600 2-year 180.10 736.00 740.87 2.43 114.53 42.20 0.12 4.87 UTtoDixon 9600 100-year 625.10 736.00 743.00 3.89 324.64 120.00 0.28 7.00 UTtoDixon 9350 1-year 126.10 733.00 740.50 0.61 457.87 173.75 0.01 7.50 UTtoDixon 9350 2-year 180.10 733.00 740.90 0.76 530.50 183.51 0.01 7.90 UTtoDixon 9350 100-year 625.10 733.00 743.05 1.46 982.06 228.14 0.04 10.05 UTtoDixon 9120 1-year 126.10 731.00 740.50 0.53 308.57 223.95 0.00 1.38 9.50 UTtoDixon 9120 2-year 180.10 731.00 740.90 0.71 323.82 225.60 0.01 1.69 9.90 1 HEC-RAS Plan:Pr River:UTtoDixon Reach:UTtoDixon(Continued) Reach River Sta Profile Q Total Min Ch El W.S.Elev Val Chnl Flow Area Top Width Shear Chan Crit Depth Max Chl Dpth (cfs) (ft) (ft) (ft/s) (sq ft) (ft) (lb/sq ft) (ft) (ft) UTtoDixon 9120 100-year 625.10 731.00 743.00 1.99 403.11 242.34 0.06 3.53 1200. UTtoDixon 9105 Culvert UTtoDixon 9075 1-year 126.10 730.00 731.73 6.60 19.65 15.78 2.06 1.73 1.73 UTtoDixon 9075 2-year 180.10 730.00 732.13 7.24 26.52 18.61 2.29 2.131 2.13 UTtoDixon 9075 100-year 625.10 730.00 734.19 9.04 92.54 111.13 2.77 4.191 4.19 UTtoDixon 9000 1-year 126.10 727.57 730.07 5.53 22.87 13.27 0.90 2.12 2.50 UTtoDixon 9000 2-year 180.10 727.57 730.45 6.53 28.08 14.51 1.17 2.54 2.88 UTtoDixon 9000 100-year 625.10 727.57 732.74 7.72 143.36 119.08 1.29 5.17 5.17 UTtoDixon 8600 1-year 126.10 723.00 725.06 6.68 18.98 15.46 1.41 2.06 2.06 UTtoDixon 8600 2-year 180.10 723.00 725.45 7.45 25.20 16.59 1.62 2.45 2.45 UTtoDixon 8600 100-year 625.10 723.00 728.63 7.12 163.76 141.58 1.06 5.63 5.63 UTtoDixon 8200 1-year 820.10 717.00 722.77 4.04 287.21 88.35 0.33 5.77 UTtoDixon 8200 2-year 1415.10 717.00 724.51 4.36 447.06 96.15 0.35 7.51 UTtoDixon 8200 100-year 1724.10 717.00 725.69 4.08 617.18 182.27 0.29 8.69 UTtoDixon 7800 1-year 820.10 716.00 721.09 8.53 125.86 46.00 1.59 5.09 UTtoDixon 7800 2-year 1415.10 716.00 723.16 8.44 226.75 51.78 1.36 7.16 UTtoDixon 7800 100-year 1724.10 716.00 724.05 10.06 276.29 87.79 1.85 6.32 8.05 UTtoDixon 7600 1-year 820.10 714.00 720.89 5.45 220.26 49.67 0.57 6.89 UTtoDixon 7600 2-year 1415.10 714.00 722.82 6.94 327.01 61.97 0.85 8.82 UTtoDixon 7600 100-year 1724.10 714.00 723.70 7.50 389.87 76.14 0.95 9.70 UTtoDixon 7400 1-year 820.10 713.00 720.38 6.40 182.69 39.75 0.78 7.38 UTtoDixon 7400 2-year 1415.10 713.00 722.03 8.58 253.51 48.13 1.30 9.03 UTtoDixon 7400 100-year 1724.10 713.00 722.83 9.32 293.32 51.33 1.49 9.83 UTtoDixon 7150 1-year 820.10 714.00 719.65 7.07 161.15 46.74 1.00 4.30 5.65 UTtoDixon 7150 2-year 1415.10 714.00 721.35 8.51 249.69 57.50 1.32 6.02 7.35 UTtoDixon 7150 100-year 1724.10 714.00 722.03 9.60 290.30 82.24 1.64 6.34 8.03 UTtoDixon 7125 Bridge UTtoDixon 7050 1-year 820.10 712.10 718.72 5.25 222.35 57.62 0.53 4.25 6.62 UTtoDixon 7050 2-year 1415.10 712.10 720.30 6.72 324.93 92.86 0.81 5.57 8.20 UTtoDixon 7050 100-year 1724.10 712.10 720.99 7.06 377.69 102.97 0.87 6.24 8.89 UTtoDixon 6950 1-year 820.10 712.00 718.08 7.47 149.73 46.39 1.13 6.08 UTtoDixon 6950 2-year 1415.10 712.00 719.57 9.01 260.68 120.62 1.51 6.39 7.57 UTtoDixon 6950 100-year 1724.10 712.00 720.23 9.58 347.86 150.51 1.66 6.89 8.23 UTtoDixon 6616 1-year 820.10 710.76 716.71 6.69 169.79 54.33 1.81 5.95 UTtoDixon 6616 2-year 1415.10 710.76 717.83 8.88 237.48 65.11 3.00 7.07 UTtoDixon 6616 100-year 1724.10 710.76 718.33 9.72 270.97 69.34 3.51 7.57 UTtoDixon 6209 1-year 820.10 707.33 713.79 7.59 183.48 107.02 2.47 5.83 6.46 UTtoDixon 6209 2-year 1415.10 707.33 717.52 3.65 792.76 307.12 0.49 10.19 UTtoDixon 6209 100-year 1724.10 707.33 718.30 3.34 1047.12 342.74 0.40 10.97 UTtoDixon 6011 1-year 820.10 705.77 711.24 9.40 109.88 40.28 3.67 4.90 5.47 UTtoDixon 6011 2-year 1415.10 705.77 717.34 3.74 1003.02 403.14 0.45 11.57 UTtoDixon 6011 100-year 1724.10 705.77 718.19 3.26 1348.96 414.51 0.33 12.42 UTtoDixon 5656 1-year 820.10 702.55 711.10 3.59 372.47 67.78 0.47 8.55 UTtoDixon 5656 2-year 1415.10 702.55 717.21 2.86 833.90 83.45 0.25 14.66 UTtoDixon 5656 100-year 1724.10 702.55 718.01 3.25 902.37 85.96 0.32 15.46 UTtoDixon 5602 1-year 820.10 701.00 710.56 5.84 140.38 51.63 1.25 4.71 9.56 UTtoDixon 5602 2-year 1415.10 701.00 716.60 6.12 231.05 78.18 1.16 6.72 15.60 UTtoDixon 5602 100-year 1724.10 701.00 717.18 7.19 239.70 79.43 1.58 7.64 16.18 UTtoDixon 5521 Culvert UTtoDixon 5418 1-year 820.10 696.00 700.64 8.79 120.43 65.10 3.75 4.64 4.64 UTtoDixon 5418 2-year 1415.10 696.00 701.51 10.53 171.87 69.85 5.07 5.51 5.51 UTtoDixon 5418 100-year 1724.10 696.00 701.90 11.21 194.70 72.66 5.60 5.90 5.90 UTtoDixon 5255 1-year 820.10 693.04 698.27 8.61 124.69 66.82 1.61 5.23 5.23 UTtoDixon 5255 2-year 1415.10 693.04 699.35 9.53 220.18 105.80 1.83 6.31 6.31 2 HEC-RAS Plan:Pr River:UTtoDixon Reach:UTtoDixon(Continued) Reach River Sta Profile Q Total Min Ch El W.S.Elev Val Chnl Flow Area Top Width Shear Chan Crit Depth Max Chl Dpth (cfs) (ft) (ft) (ft/s) (sq ft) (ft) (lb/sq ft) (ft) (ft) UTtoDixon 5255 100-year 1724.10 693.04 699.68 10.15 255.90 112.83 2.04 6.64 6.64 UTtoDixon 4732 1-year 820.10 688.41 693.00 9.22 98.19 53.80 2.00 4.46 4.59 UTtoDixon 4732 2-year 1415.10 688.41 694.34 9.91 191.96 75.03 2.07 5.93 5.93 UTtoDixon 4732 100-year 1724.10 688.41 694.88 10.16 233.30 76.67 2.10 6.47 6.47 UTtoDixon 4414 1-year 820.10 686.37 691.34 6.93 127.75 48.47 1.07 4.97 UTtoDixon 4414 2-year 1415.10 686.37 693.00 7.08 253.03 120.06 0.99 6.63 UTtoDixon 4414 100-year 1724.10 686.37 692.95 8.77 247.44 118.76 1.53 6.21 6.58 UTtoDixon 4042 1-year 820.10 684.25 689.71 7.16 127.38 41.48 1.09 5.46 UTtoDixon 4042 2-year 1415.10 684.25 690.43 10.32 159.75 49.57 2.15 5.84 6.18 UTtoDixon 4042 100-year 1724.10 684.25 691.65 8.26 381.48 310.69 1.29 7.39 7.39 UTtoDixon 3616 1-year 820.10 683.12 688.25 6.90 277.63 300.37 1.02 5.13 5.13 UTtoDixon 3616 2-year 1415.10 683.12 688.66 8.25 405.94 325.59 1.42 5.54 5.54 UTtoDixon 3616 100-year 1724.10 683.12 688.81 8.86 454.66 329.48 1.63 5.69 5.69 UTtoDixon 3129 1-year 820.10 680.27 685.06 8.22 118.57 107.94 1.52 4.36 4.79 UTtoDixon 3129 2-year 1415.10 680.27 686.25 7.14 397.89 378.77 1.05 5.98 5.98 UTtoDixon 3129 100-year 1724.10 680.27 686.45 7.37 476.09 384.28 1.11 6.18 6.18 UTtoDixon 2685 1-year 820.10 677.41 682.94 4.91 176.29 68.45 1.12 4.21 5.53 UTtoDixon 2685 2-year 1415.10 677.41 684.04 5.82 360.70 266.29 1.44 5.12 6.63 UTtoDixon 2685 100-year 1724.10 677.41 684.58 6.24 525.78 344.91 1.60 5.56 7.17 3 Dixon Branch Limited Detail Study Plan: PrSteady 12/29/2023 900 UTtoDixon UTtoDixon A� Legend WS 100-year • WS 2-year WS 1-year t Ground 850 B Left Levee 800 c 0 w 750 700 650 0 2000 4000 6000 8000 10000 12000 Main Channel Distance(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS= 13275 .08 �.1 880 0 Legend 3 5 875 WS 1-year WS 2-year 870 WS 100-year 865 Ground > • w 860 Bank Sta 855 850 4800 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=13209 14 083 .04�. .1 880 0 Legend 3 5 875 WS 1-year WS 2-year 870 WS 100-year 865 Ground > w Levee 860 A Ineff • 855 Bank Sta 850 4800 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=13159 Culy 14 083 .04�. .1 880 0 Legend 3 5 875 WS 1-year WS 2-year 870 WS 100-year 865 Ground > w Levee 860 A Ineff • 855 Bank Sta 850 4800 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS= 12929 880 .08 0 F 1 Legend 3 875 5 ~ WS 100-year • 870 WS 2-year 865 0 WS 1-year Ground > 860 A w Ineff 855 • Bank Sta 850 845 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=12886 880 .1 .1 O8 0 3 Legend 875 WS 100- reay 870 WS 2-year 865 WS 1-year 860 Ground w 855 Ineff • 850 Bank Sta 845 840 � 4800 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=12876 Culy 880 .1 .1 O8 0 3 Legend 875 WSWS1� 870 WS 2-year 865 WS 1-year 860 Ground w 855 Ineff • 850 Bank Sta 845 840 4800 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS= 12835 875 �.08 .04�O�.1 3 Legend 870 5 ~ WS 100-year • 865 WS 2-year 860 0 WS 1-year Ground > 855 A w Ineff 850 Bank Sta 845 840 4800 4850 4900 4950 5000 5050 5100 5150 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=12775 875 �'08 .04 O 1 3 Legend 870 5 ~ WS 100-year 865 WS 2-year 860 WS 1-year 0 855 Ground > w 850 Bank Sta 845 840 835 4800 4850 4900 4950 5000 5050 5100 5150 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=12600 880 �.1��.08 0 1 3 Legend 5 870 WS 100-year • WS 2-year 860 WS 1-year 0 Ground w 850 Bank Sta 840 830 4700 4800 4900 5000 5100 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS= 12200 860 1��.04 .04 .1 3 Legend 855 WSWS1� 850 WS 2-year 845 WS 1-year 840 Ground > w 835 Bank Sta 830 825 820 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=11885 860 �.1�0�.04 T .1 3 Legend 5 850 WS 100-year • WS 2-year 840 WS 1-year 0 Ground w 830 Bank Sta 820 810 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=11600 �.1��.04�. 1 870 3 Legend 5 860 WS 100-year • WS 2-year 850 WS 1-year 840 Ground > w 830 Bank Sta 820 810 4800 4900 5000 5100 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS= 11200 840 1 O 1 3 Legend 5 830 WS 100-year • WS 2-year 820 WS 1-year 810 Ground > w 800 Bank Sta 790 780 4850 4900 4950 5000 5050 5100 5150 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=11000 840 1 O .08 .1 3 Legend 830 5 ~ WS 100-year • 820 WS 2-year 810 0 WS 1-year Ground w 800 Bank Sta 790 780 770 4700 4800 4900 5000 5100 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=10600 .1 .1 810 0 Legend 3 � 800 5 WS 100-year • WS 2-year 790 WS 1-year ° 780 Ground > 0 w 770 Bank Sta 760 750 4850 4900 4950 5000 5050 5100 5150 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS= 10200 820 F �0�.04 .08 .1 3 Legend 810 5 ~ WS 100-year 800 WS 2-year 790 WS 1-year 0 780 Ground > w 770 Bank Sta 760 750 740 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=10000 800 .1 0�.08 .1 3 Legend � 790 5 WS 100-year • WS 2-year 780 WS 1-year 0 ° 770 Ground > w 760 Bank Sta 750 740 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=9600 790 �.1�0�.04 .08� 3 Legend � 780 5 WS 100-year • WS 2-year 770 WS 1-year 0 ° 760 Ground > w 750 Bank Sta 740 730 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=9350 780 F "�.04�0�.08 3 Legend 5 770 WS 100-year • WS 2-year 760 WS 1-year 0 Ground w 750 Bank Sta 740 730 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=9120 780 �.1��.04�0� .1 3 Legend 5 770 WS 100-year • WS 2-year 760 WS 1-year 0 Ground > 2 750 Ineff w • Bank Sta 740 730 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=9105 Culy 780 �.1��.04�OF .1 3 Legend 5 770 WS 100-year • WS 2-year 760 WS 1-year 0 Ground > w 750 Ineff • Bank Sta 740 730 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=9075 770 �.1��.04 O 1 3 Legend 5 � WS 100-year 760 WS 2-year WS 1-year 750 Ground > w Ineff • 740 Bank Sta 730 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=9000 770 �.1��.04 0�.08� 1 3 Legend 5 760 WS 100-year • WS 2-year — 750 WS 1-year 0 Ground w 740 Bank Sta 730 720 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=8600 �770 .1��.04 J 1 Legend 3 5 760 WS 100-year • WS 2-year — 750 WS 1-year 0 Ground 2 740 � w - Levee Bank Sta 730 720 4400 4600 4800 5000 5200 5400 5600 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=8200 780 �.1 '�.04�. 04 .08� 3 Legend 770 5 ~ WS 100-year • 760 WS 2-year 750 WS 1-year 0 Ground w 740 Bank Sta 730 720 710 4600 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=7800 790 1��.04 0 .1 3 Legend 780 5 ~ WS 100-year 770 WS 2-year 760 WS 1-year 750 Ground > w 740 Bank Sta 730 720 710 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=7600 790 �.1 0 3 Legend 780 WSWS1� 770 WS 2-year 760 WS 1-year ° 750 Ground > w 740 Bank Sta 730 720 710 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=7400 790 08 0 .O8 3 Legend 780 WSWS1� 770 WS 2-year 760 WS 1-year 750 Ground > • w 740 Bank Sta 730 720 710 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=7150 770 �-.08 .0 4�O 5 .08 3 Legend 5 760 WS 100-year • WS 2-year 750 WS 1-year 740 Ground > w 730 Ineff • Bank Sta 720 710 � 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=7125 BR .08 .0 770 4�O .08 3 Legend 5 760 WS 100-year • WS 2-year 750 WS 1-year 740 Ground > w Ineff 730 • Bank Sta 720 710 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=7050 770 .1 �.08�O�.04 �.1 3 Legend � 760 5 WS 100-year • WS 2-year 750 WS 1-year 740 Ground > w 730 Ineff • Bank Sta 720 710 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=6950 770 � .04 O 1 3 Legend 5 760 WS 100-year • WS 2-year 750 WS 1-year 740 Ground > • w 730 Bank Sta 720 710 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=6616 760 1 ��.035 .08�O O .035�F .1 5 8 Legend 750 WS 100-year • WS 2-year — 740 WS 1-year 0 Ground 730 Bank Sta w 720 710 4700 4800 4900 5000 5100 5200 5300 5400 5500 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=6209 760 � 1��.035��.08�0 .1 5 Legend 750 WS 100-year • WS 2-year 740 WS 1-year ° 730 Ground > w 720 Bank Sta 710 700 4600 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=6011 770 �.1 ��.04 0 .08 1� 5 Legend 760 WS 100- reay • 750 WS 2-year WS 1-year c 740 0 •� Ground 730 w Bank Sta 720 710 700 4700 4800 4900 5000 5100 5200 5300 5400 5500 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=5656 750 �.0" .08 0 08 5 Legend 740 WS 100-year • WS 2-year — 730 WS 1-year 0 Ground w 720 Bank Sta 710 700 4850 4900 4950 5000 5050 5100 5150 5200 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=5602 780 .05___ 0 5 Legend 770 ~ WS 100-year 760 WS 2-year 750 "-- WS 1-year 740 Ground > w 730 Ineff • 720 Bank Sta 710 700 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=5521 Culy 780 .1��.05 0 .1 Legend 5 770 ~ WS 100-year 760 WS 2-year 750 WS 1-year 740 Ground > w 730 Ineff • 720 Bank Sta 710 700 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=5418 770 1��.08 0�0 .08 5 Legend 760 ~ WS 100-year 750 WS 2-year 740 WS 1-year 730 Ground w 720 Ineff • 710 Bank Sta 700 690 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=5255 1 .04 .035 .1 800 3 Legend � 780 5 WS 100-year WS 2-year 760 WS 1-year 0 740 Ground > w 720 Bank Sta 700 680 4400 4600 4800 5000 5200 5400 5600 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=4732 740 '035+—.08 O .04 1 3 Legend � 730 5 WS 100-year WS 2-year 720 WS 1-year ° 710 Ground > w 700 Bank Sta 690 680 4800 4900 5000 5100 5200 5300 5400 5500 5600 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=4414 730 .035—+—.08��.04 .035+.035��.08 Legend 720 WS 2-year WS 100- reay — 710 WS 1-year 0 Ground 700 Bank Sta w 690 680 4500 4600 4700 4800 4900 5000 5100 5200 5300 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=4042 740 .04 "� . .04��.035 3 Legend 5 730 WS 100-year • WS 2-year 720 WS 1-year ° 710 Ground > w 700 Bank Sta 690 680 4500 4600 4700 4800 4900 5000 5100 5200 5300 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=3616 740 1 .04 t]1.05 3 Legend � 730 5 WS 100-year • WS 2-year 720 WS 1-year ° 710 Ground > w 700 Bank Sta 690 680 4400 4600 4800 5000 5200 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=3129 730 •035 .08��.04 1 .O .04 3 Legend 5 720 WS 100-year • WS 2-year — 710 WS 1-year 0 Ground 700 Bank Sta w 690 680 4400 4600 4800 5000 5200 5400 Station(ft) Dixon Branch Limited Detail Study Plan: PrSteady RS=2685 1 04 740 0 Legend 5 730 WS 1 p-year • 720 WS 2-year 710 WS 1-year 0 � Ground w 700 Bank Sta 690 680 670 4400 4600 4800 5000 5200 5400 Station(ft) SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Appendices Appendix D-2: Channel Design Calculations DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 TABLE B-1 BASIN SUMMARY TABLE Albemarle Kings Mountain PFS Archdale Channel Design Date: 4/3/24 PROJECT NO.: USPR000576 By: DPH Chkd: DESIGN STORM: PMP RECURRENCE INTERVAL Apprvd: 2-YEAR STORM DURATION DEPTH PMP DEPTH Storm (hours) (in) (in) Distribution Model Units 24 3.63 28.50 1 Imperial CN=82 CN=76 CN=60 CN=72 CN 72 CN=100 Reclaimed Offsite Composite Unit Runoff Runoff AREA Roadway/Pad Berm Tailings Drainage Highway Verge Impervious SCS Curve S= Q Volume SUBBASIN ID (ac) (ac) (ac) (ac) (ac) (ac) (ac) No. 1000/CN-10 (in) (ac-ft) Contact Pond 2.240 0.00 1.16 0.00 0.00 0.00 1.08 CN=88 1.42 26.86 5.01 CutSlope 1 0.510 0.00 0.51 0.00 0.00 0.00 0.00 CN=76 3.16 25.03 1.06 CutSlope 2 0.580 0.00 0.58 0.00 0.00 0.00 0.00 CN=76 3.16 25.03 1.21 CutSlope 3 0.290 0.00 0.29 0.00 0.00 0.00 0.00 CN=76 3.16 25.03 0.60 Offsite 1 3.260 0.00 1.91 0.00 1.35 0.00 0.00 CN=74 3.45 24.74 6.72 Offsite 2 7.560 0.00 0.00 0.00 7.56 0.00 0.00 CN=72 3.89 24.31 15.32 Offsite 3 7.460 0.00 0.00 0.00 7.46 0.00 0.00 CN=72 3.89 24.31 15.11 Offsite 4 9.800 0.00 0.00 0.00 9.80 0.00 0.00 CN=72 3.89 24.31 19.85 Offsite 5 1.470 0.00 0.00 0.00 1.47 0.00 0.00 CN=72 3.89 24.31 2.98 Offsite 6 20.490 0.00 0.35 0.00 12.06 8.08 0.00 CN=72 3.88 24.32 41.53 Offsite 7 5.110 0.00 0.18 0.00 0.00 4.93 0.00 CN=72 3.86 24.34 10.36 Offsite 8 4.680 0.00 0.61 0.00 0.00 4.07 0.00 CN=73 3.79 24.41 9.52 Pad 1 1.760 1.76 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 3.82 Pad 2 1.350 1.35 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 2.93 Pad 3 1.150 1.15 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 2.49 Pad 4 3.450 3.45 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 7.48 Pad 5 0.280 0.28 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 0.61 Pad 6 0.910 0.91 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 1.91 Pad 7 0.420 0.42 0.00 0.00 0.00 0.00 0.00 CN=82 2.20 26.03 0.91 Perim 1 11.469 2.76 8.71 0.00 0.00 0.00 0.00 CN=77 2.91 25.28 24.16 Perim 2 4.496 1.73 2.77 0.00 0.00 0.00 0.00 CN=78 2.77 25.43 9.53 Perim 3 0.848 0.76 0.09 0.00 0.00 0.00 0.00 CN=81 2.29 25.93 1.83 Perim 4 2.229 0.52 0.42 0.00 0.00 1.29 0.00 CN=75 3.32 24.87 4.62 Perim 5 11.107 2.73 1.63 0.00 0.00 5.50 1.25 CN=78 2.79 25.41 23.52 Perim 6 5.506 1.26 0.91 0.00 0.00 2.64 0.69 CN=78 2.74 25.45 11.68 Perim 7 13.603 2.52 2.66 0.00 0.00 7.12 1.31 CN=77 2.93 25.26 28.64 Perim 8 5.795 1.10 1.88 0.00 0.00 2.33 0.49 CN=78 2.89 25.30 12.22 Perim 9 5.276 1.79 3.49 0.00 0.00 0.00 0.00 CN=78 2.81 25.38 11.16 Sed Pond 0.700 0.00 0.20 0.00 0.00 0.00 0.50 CN=93 0.73 27.64 1.61 TSF 56.277 0.00 0.00 56.28 0.00 0.00 0.00 CN=60 6.67 21.81 102.30 Total: 190.08 380.77 Page 1 of 1 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xism 4/3/2024 TABLE B-2 BASIN TIME OF CONCENTRATION CALCULATIONS Albemarle Kings Mountain PFS Date: 4/3/24 Archdale Channel Design By:DPH PROJECT NO.: USPR000576 Chkd: Apprvd: Flow Segment 1 Flow Segment 2 Total Total Typical Hydraulic Typical Hydraulic Lag Travel Radius Travel Radius Travel Basin Area Composite (0.6*Tc) Time Type of Length Slope (Channel Only) Time Type of Length Slope (Channel Only) Time SUBBASIN ID (sq mi) Curve Number (min) (min) Flow (ft) (eft) Rou hness Condition(l) (ft) (min) Flow (ft) (eft) Roughness Condition(') (ft) (min) Contact Pond 0.0035 88 20.4 34 Sheet 20 0.400 G Bermuda Grass 1.71 Shallow 30 0.010 P Paved 0.25 CutSlope 1 0.0008 76 2.1 4 Sheet 30 0.400 G Bermuda Grass 2.37 CutSlope 2 0.0009 76 4.0 7 Sheet 80 0.400 G Bermuda Grass 5.19 CutSlope 3 0.0005 76 3.4 6 Sheet 80 0.400 G Bermuda Grass 5.19 Offsite 1 0.0051 74 5.8 10 Sheet 75 0.320 J Heavy Woods 9.20 Shallow 150 0.320 B Bare 0.44 Offsite 2 0.0118 72 20.8 35 Sheet 75 0.070 J Heavy Woods 16.90 Shallow 650 0.070 F Forest 16.27 Offsite 3 0.0117 72 35.2 59 Sheet 75 0.015 J Heavy Woods 31.29 Shallow 500 0.015 F Forest 27.04 Offsite 4 0.0153 72 33.4 56 Sheet 75 0.035 J Heavy Woods 22.29 Shallow 600 0.015 F Forest 32.45 Offsite 5 0.0023 72 15.9 27 Sheet 75 0.088 J Heavy Woods 15.42 Shallow 425 0.088 F Forest 9.49 Offsite 6 0.0320 72 23.5 39 Sheet 75 0.057 J Heavy Woods 18.34 Shallow 650 0.057 F Forest 18.03 Offsite 7 0.0080 72 8.2 14 Sheet 75 0.057 G Bermuda Grass 10.75 Shallow 125 0.057 G Grass 0.54 Offsite 8 0.0073 73 10.3 17 Sheet 75 0.090 G Bermuda Grass 8.95 Shallow 100 0.0900 G Grass 0.34 Pad 1 0.0028 82 2.8 5 Sheet 75 0.020 A Smooth 0.90 Shallow 190 0.0200 P Paved 1.10 Pad 2 0.0021 82 0.8 1 Sheet 75 0.020 A Smooth 0.90 Shallow 70 0.0200 P Paved 0.41 Pad 3 0.0018 82 1.2 2 Sheet 75 0.020 A Smooth 0.90 Shallow 60 0.0200 P Paved 0.35 Pad 4 0.0054 82 1.3 2 Sheet 75 0.020 A Smooth 0.90 Shallow 225 0.0200 P Paved 1.30 Pad 5 0.0004 82 1.0 2 Sheet 75 0.020 A Smooth 0.90 Shallow 50 0.0200 P Paved 0.29 Pad 6 0.0014 82 1.4 2 Sheet 75 0.020 A Smooth 0.90 Shallow 125 0.0200 P Paved 0.72 Pad 7 0.0007 82 0.9 2 Sheet 75 0.020 A Smooth 0.90 Shallow 65 0.020 P Paved 0.38 Perim 1 0.0179 77 4.2 7 Sheet 13 0.400 B Fallow 0.23 Perim 2 0.0070 78 1.4 2 Sheet 13 0.400 B Fallow 0.23 Perim 3 0.0013 81 0.8 1 Sheet 20 0.400 B Fallow 0.32 Perim 4 0.0035 75 6.4 11 Sheet 37 0.400 B Fallow 0.52 Perim 5 0.0174 78 0.8 1 Sheet 42 0.400 B Fallow 0.58 Perim 6 0.0086 78 3.3 6 Sheet 55 0.400 B Fallow 0.71 Perim 7 0.0213 77 1.3 2 Sheet 87 0.400 B Fallow 1.03 Perim 8 0.0091 78 5.2 9 Sheet 75 0.400 B Fallow 0.92 Shallow 50 0.400 B Bare 0.13 Perim 9 0.0082 78 21.6 36 Sheet 55 0.400 G Bermuda Grass 3.85 Sed Pond 0.0011 93 2.8 5 Notes: (1)Refer to Attachment B for Flow calculations, Roughness Condition descriptions and Tc Coefficients Page 1 of 2 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xism 4/3/2024 TABLE B-2 BASIN TIME OF CONCENTRATION CALCULATIONS Albemarle Kings Mountain PFS Date: 4/3/24 Archdale Channel Design By:DPH PROJECT NO.: USPR000576 Chkd: Apprvd: Flow Segment 3 Flow Segment 4 Total Total Typical Hydraulic Typical Hydraulic Lag Travel Radius Travel Radius Travel Basin Area Composite (0.6*Tc) Time Type of Length Slope (Channel Only) Time Type of Length Slope (Channel Only) Time SUBBASIN ID (sq mi) Curve Number (min) (min) Flow (ft) (eft) Rou hness Condition(l) (ft) (min) Flow (ft) (eft) Roughness Condition(") (ft) (min) Contact Pond 0.0035 88 20.4 34 Channel 300 0.001 P Plastic 0.01 3209. CutSlope 1 0.0008 76 2.1 4 Channel 500 0.028 G Grass-lined 1.00 1.17 CutSlope 2 0.0009 76 4.0 7 Channel 625 0.028 G Grass-lined 1.00 1.47 CutSlope 3 0.0005 76 3.4 6 Channel 125 0.028 G Grass-lined 0.50 0.47 Offsite 1 0.0051 74 5.8 10 Offsite 2 0.0118 72 20.8 35 Channel 525 0.020 G Grass-lined 1.00 1.46 Offsite 3 0.0117 72 35.2 59 Channel 280 0.070 G Grass-lined 1.00 0.42 Offsite 4 0.0153 72 33.4 56 Channel 620 0.060 G Grass-lined 1.00 0.99 Offsite 5 0.0023 72 15.9 27 Shallow 16 0.4000 G Grass 0.03 Channel 590 0.020 G Grass-lined 1.00 1.64 Offsite 6 0.0320 72 23.5 39 Shallow 130 0.0900 G Grass 0.45 Channel 960 0.026 G Grass-lined 1.00 2.34 Offsite 7 0.0080 72 8.2 14 Channel 980 0.028 G Grass-lined 1.00 2.30 Offsite 8 0.0073 73 10.3 17 Channel 640 0.001 G Grass-lined 1.00 7.94 Pad 1 0.0028 82 2.8 5 Shallow 175 0.0200 P Paved 1.01 Channel 710 0.028 G Grass-lined 1.00 1.67 Pad 2 0.0021 82 0.8 1 Pad 3 0.0018 82 1.2 2 Channel 320 0.028 G Grass-lined 1.00 0.75 Pad 4 0.0054 82 1.3 2 Pad 5 0.0004 82 1.0 2 Channel 180 0.028 G Grass-lined 1.00 0.42 Pad 6 0.0014 82 1.4 2 Channel 210 0.028 G Grass-lined 0.50 0.78 Pad 7 0.0007 82 0.9 2 Channel 75 0.028 G Grass-lined 0.50 0.28 Perim 1 0.0179 77 4.2 7 Channel 1255 0.005 G Grass-lined 1.00 6.83 Perim 2 0.0070 78 1.4 2 Channel 555 0.010 G Grass-lined 1.00 2.18 Perim 3 0.0013 81 0.8 1 Channel 375 0.020 G Grass-lined 1.00 1.04 Perim 4 0.0035 75 6.4 11 Channel 1840 0.005 G Grass-lined 1.00 10.21 Perim 5 0.0174 78 0.8 1 Channel 611 0.0850 G Grass-lined 1.00 0.82 Perim 6 0.0086 78 3.3 6 Channel 1220 0.0100 G Grass-lined 1.00 4.79 Perim 7 0.0213 77 1.3 2 Channel 532 0.0485 R Riprap 1.00 1.08 Perim 8 0.0091 78 5.2 9 Shallow 25 0.4000 G Grass 0.04 Channel 870 0.0020 G Grass-lined 1.00 7.64 Perim 9 0.0082 78 21.6 36 Channel 300 0.001 P Plastic 0.01 3209. Sed Pond 0.0011 93 2.8 5 Channel 532 0.0020 G Grass-lined 1.00 4.67 Notes: (1)Refer to Attachment B for Flow calculations, Roughness Condition descriptions and Tc Coefficients Page 2 of 2 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xism 4/3/2024 TABLE B-3a FLOW RESULTS FROM HEC-HMS Albemarle Kings Mountain PFS Archdale Channel Design Date: 4/3/24 PROJECT NO.:USPR000576 By:DPH Chkd: HMS Run Description 10 YR (Data Range Name:HECHMS_10_YR) V Copy entire HTML Output from Standard Report(Global results ONLY)and paste in cell beloo Project:Archdale_Perimeter_v2 Simulation Run:Archdale 10yr Simulation Start:31 December 2023,24:00 Simulation End:2 January 2024,12:00 HMS Version:4.11 Executed:28 March 2024,22:27 Global Results Summary Drainage Area Peak Discharge Hydrologic Element (M12) (CFS) Time of Peak Volome(IN) Archdale SedPwa 0.0954 70.5 1 January 2024,13:01 3.11 Contact Ponc 0.0035 3 1 January 2024,13:02 4.15 Contact Pond Storage 0.0914 1.3 1 January 2024,13:10 0.5 Culvert-30inlei 0.113 14.42 1 January 2024,13:02 0.94 Culvert-36inlei 0.0817 48.76 1 January 2024,13:01 2.68 Culvert-60Inlel 0.1027 73.8 1 January 2024,13:03 3.07 CutSlopel 0.0008 0.58 1 January 2024,13:00 2.95 CutSlope2 0.0009 0.65 1 January 2024,13:00 2.95 CutSlope3 0.0005 0.36 1 January 2024,13:00 2.95 C-PTIIA 0.0083 6.27 1 January 2024,13:07 3.18 C-PT11B 0.0013 1.06 1 January 2024,13:10 3.43 C-PT121, 0.0035 2.49 1 January 2024,13:08 2.86 C-PT 12c 0.0209 15.45 1 January 2024,13:02 3.09 C-PT12d 0.0295 21.86 1 January 2024,13:03 3.11 C-PT12c 0.0508 37.47 1 January 2024,13:01 3.08 C-PT12f 0.0599 44.21 1 January 2024,13:01 3.09 NC-CULV-TPADI 0.0397 23.3 1 January 2024,13:04 2.6 NC-CULV-TPAD2 0.0059 4.1 1 January 2024,13:01 2.79 NC_Pad6 0.0028 1.81 1 January2024,13:03 2.65 NC_SWALE2 0.0014 1.14 1 January2024,13:01 3.53 N_C-PT11a 0.0262 19.26 1 January2024,13:01 3.09 N_C-PT1lb 0.0083 6.29 1 January2024,13:00 3.19 N_C-PT11c 0.0013 1.04 1 January2024,13:00 3.43 N_C-PT12a 0.0035 2.51 1 January2024,13:00 2.86 N_C-PT12b 0.0209 15.46 1 January2024,13:00 3.09 N_C-PT12c 0.0295 21.9 1 January2024,13:00 3.11 N_C-PT12d 0.0508 37.48 1 January2024,13:00 3.08 N_C-PT12c 0.0599 44.28 1 January2024,13:00 3.09 N_C-PT12f 0.0681 50.35 1 January2024,13:00 3.1 N_NCOS8 0.0077 6.22 1 January2024,13:00 3.53 N_NC-SWALE4 0.0049 3.96 1 January 2024,13:00 3.53 N_NC-TPad5 0.0028 1.82 1 January 2024,13:00 2.65 N NC Pad4 0.0082 6.17 1 January 2024,13:00 3.23 N_NC_Swalel 0.01 7.63 1 January2024,13:00 3.28 N_NC_Swale2 0.0014 1.13 1 January 2024,13:00 3.53 N_NC_SWALE3 0.0035 2.83 1 January 2024,13:00 3.53 N_TPADI-INLET 0.0397 23.3 1 January2024,13:03 2.6 N_TPAD2-INLET 0.0059 4.1 1 January 2024,13:00 2.79 OffsBe-1 0.0051 3.52 1 January 2024,13:00 2.77 Offsite-2 0.0118 7.34 1 January 2024,13:04 2.59 Offsite-3 0.0117 6.77 1 January 2024,13:11 2.59 Offsite-4 0.0153 8.94 1 January 2024,13:10 2.59 Offsite-5 0.0023 1.46 1 January 2024,13:02 2.59 Offsite-6 0.032 19.66 1 January 2024,13:05 2.59 Offsite-7 0.008 5.23 1 January 2024,13:01 2.59 Offsite-8 0.0073 4.85 1 January 2024,13:01 2.68 Outfall 30 0.113 15.54 1 January 2024,13:00 0.98 Outfall 36 0.0817 50.05 1 January 2024,13:00 2.68 Outfall-60 0.1027 75.35 1 January 2024,13:01 3.08 Pad 1 0.0028 2.26 1 January 2024,13:00 3.53 Pad 2 0.0021 1.7 1 January 2024,13:00 3.53 Pad 3 0.0018 1.46 1 January 2024,13:00 3.53 Pad 4 0.0054 4.37 1 January 2024,13:00 3.53 Pad 5 0.0007 0.57 1 January 2024,13:00 3.53 Pad 6 0.0014 1.13 1 January 2024,13:00 3.53 Pad? 0.0007 0.57 1 January 2024,13:00 3.53 Perim l 0.0179 13.07 1 January 2024,13:00 3.05 Perim 2 0.007 5.27 1 January 2024,13:00 3.14 Perim 3 0.0013 1.04 1 January 2024,13:00 3.43 Perim 4 0.0035 2.51 1 January 2024,13:00 2.86 Perim 5 0.0174 13.01 1 January 2024,13:00 3.14 Perim 6 0.0086 6.52 1 January 2024,13:00 3.14 Perim 7 0.0213 15.76 1 January 2024,13:00 3.05 Perim 8 0.0091 6.89 1 January 2024,13:00 3.14 Perim 9 0.0082 6.15 1 January 2024,13:00 3.14 Perim Culven 0.0943 69.6 1 January2024,13:00 3.09 Perim Sink 0.2974 136.85 1 January2024,13:02 2.15 Sed Pond 0.0011 1 1 January 2024,13:01 4.69 SWale4 0.0035 2.84 1 January 2024,13:01 3.53 TSF 0.0879 41.42 1 January 2024,13:00 1.6 TSF_Suml 0.0879 1.3 1 January 2024,11:14 0.57 Page 1 of 1 SRK Consulting B.-HBH-ksheet Archdale Peron 01APR2024.%Ism 4/3/2024 TABLE B-3b FLOW RESULTS FROM HEC-HMS Albemarle Kings Mountain PFS Archdale Channel Design Date: 4/3/24 PROJECT NO.:USPR000576 By:DPH Chkd: HMS Run Description 25 YR (Data Range Name:HECHMS_25_YR) V Copy entire HTML Output from Standard Report(Global results ONLY)and paste in cell belo, Project:Archdale_Perimeter_Q Simulation Run:Archdale 25yr Simulation Start:31 December 2023,24:00 Simulation End:2 January 2024,12:00 HMS Version:4.11 Executed:28 March 2024,22:44 Global Results Summary Hydrologic Element Drainage Area Peak Discharge Time of Peak Volume(IN) (M12) (CFS) Archdale ScdPon( 0.1 89.1 OIJan2024,13:01 4.08 C-PT11A 0.01 7.89 0IJan2024,13:07 4.16 C-PTIIB 0 1.29 0IJan2024,13:07 4.43 C-PT12b 0 3.17 0IJan2024,13:07 3.8 C-PT12c 0.02 19.53 OIJan2024,13:02 4.06 C-PT12d 0.03 27.63 OIJan2024,13:03 4.08 C-PT12c 0.05 47.4 OIJan2024,13:01 4.05 C-PT12f 0.06 55.91 0IJan2024,13:00 4.06 Contact Ponc 0 3.67 0IJan2024,13:01 5.21 Contact Pond Storage 0.09 1.3 0IJan2024,12:48 0.51 Culvert-30inlel 0.11 19.49 0IJan2024,13:02 1.13 Culvert-36inlel 0.08 63 OIJan2024,13:02 3.59 Culvert-60Ialel 0.1 93.93 OIJan2024,13:02 4.03 Cut Slope 1 0 0.74 OIJan2024,13:00 3.9 Cut Slope 2 0 0.83 OIJan2024,13:00 3.9 Cut Slope 3 0 0.46 OIJan2024,13:00 3.9 N Nc Swale3 0 3.51 0IJan2024,13:00 4.54 N Ncos8 0.01 7.72 OIJan2024,13:00 4.54 N_C-PTlla 0.03 24.37 0IJan2024,13:00 4.06 N_C-PT116 0.01 7.91 0IJan2024,13:00 4.16 N_C-PTllc 0 1.29 0IJan2024,13:00 4.43 N_C-PT12a 0 3.19 0IJan2024,13:00 3.8 N_C-PT126 0.02 19.54 OIJan2024,13:00 4.06 N_C-PT12c 0.03 27.67 OIJan2024,13:00 4.08 N_C-PT12d 0.05 47.4 OIJan2024,13:00 4.05 N_C-PT12c 0.06 55.99 OIJan2024,13:00 4.06 N_C-PT12f 0.07 63.66 OIJan2024,13:00 4.06 N_NC-SWALE4 0 4.92 OIJan2024,13:00 4.54 N_NC-TPad5 0 2.35 OIJan2024,13:00 3.56 N_NC_Pad4 0.01 7.76 OIJan2024,13:00 4.21 N_NC_Swalel 0.01 9.56 0IJan2024,13:00 4.27 N_NC_Swale2 0 1.41 0IJan2024,13:00 4.54 N_TPADI-INLET 0.04 30.72 0IJan2024,13:03 3.5 N_TPAD2-INLET 0.01 5.25 0IJan2024,13:00 3.72 NC-CULV-TPADI 0.04 30.72 OIJan2024,13:04 3.5 NC-CULV-TPAD2 0.01 5.25 0IJan2024,13:01 3.72 Nc Swale2 0 1.41 0IJan2024,13:01 4.54 NC_Pad6 0 2.35 OIJan2024,13:03 3.56 Offsite-1 0.01 4.51 0IJan2024,13:00 3.7 Offsite-2 0.01 9.58 0IJan2024,13:04 3.49 Offsite-3 0.01 8.94 0IJan2024,13:10 3.49 Offsite-4 0.02 11.79 0IJan2024,13:09 3.49 Offsite-5 0 1.9 0IJan2024,13:02 3.49 Offsite-6 0.03 25.73 0IJan2024,13:05 3.49 Offsite-7 0.01 6.77 OIJan2024,13:00 3.49 Offsite-8 0.01 6.26 OIJan2024,13:01 3.59 Octfall-60 0.1 95.36 OIJan2024,13:01 4.04 Outfall30 0.11 21.03 0IJan2024,13:00 1.16 Outfall 36 0.08 65.49 0IJan2024,13:00 3.59 Pad 1 0 2.81 0IJan2024,13:00 4.54 Pad 0 2.11 0IJan2024,13:00 4.54 Pad 0 1.81 0IJan2024,13:00 4.54 Pad 0.01 5.42 0IJan2024,13:00 4.54 Pad 5 0 0.7 OIJan2024,13:00 4.54 Pad 0 1.41 OIJan2024,13:00 4.54 Pad? 0 0.7 OIJan2024,13:00 4.54 Perim 1 0.02 16.56 OIJan2024,13:00 4.01 Perim 0.01 6.63 0IJan2024,13:00 4.11 Perim 0 1.29 0IJan2024,13:00 4.43 Perim 0 3.19 0IJan2024,13:00 3.8 Perim 5 0.02 16.41 0IJan2024,13:00 4.11 Perim 0.01 8.2 0IJan2024,13:00 4.11 Perim? 0.02 19.91 0IJan2024,13:00 4.01 Perim 8 0.01 8.67 0IJan2024,13:00 4.11 Perim 0.01 7.75 OIJan2024,13:00 4.11 Perim_Culven 0.09 88.03 0IJan2024,13:00 4.06 Perim Sink 0.3 176.42 0IJan2024,13:02 2.81 S Wale 4 0 3.52 0IJan2024,13:01 4.54 SedPond 0 1.2 0IJan2024,13:01 5.78 Taf 0.09 57.05 0IJan2024,13:00 2.32 TSE_Suml 0.09 1.3 0IJan2024,11:01 0.57 Page t of t SRK Consulting B.-HBH-ksheet Archdale Peron 01APR2024.%Ism 4/3/2024 TABLE B-3c FLOW RESULTS FROM HEC-HMS Albemarle Kings Mountain PFS Archdale Channel Design Date: 4l3/24 PROJECT NO.:USPR000576 I By,IIDPH Chkd: HMS Run Description 100 YR (Data Range Name:HECHMS_100_YR) V Copy entire HTML Output from Standard Report(Global results ONLY)and paste in cell beloo Project:Archdale_Perimeter_Q Simulation Run:Archdale 100yr Simulation Start:31 December 2023,24:00 Simulation End:2 January 2024,12:00 HMS Version:4.11 Executed:28 March 2024,22:27 Global Results Summary Hydrologic Element Drainage Area Peak Discharge Time of Peak Volume(IN) (M12) (CFS) Archdale ScdPonc 0.1 119.96 OIJan2024,13:00 5.72 C-PT11A 0.01 10.58 OIJan2024,13:06 5.82 C-PTIIB 0 1.7 OIJan2024,13:06 6.12 C-PT12b 0 4.31 OIJan2024,13:07 5.4 C-PT12c 0.02 26.3 OIJan2024,13:02 5.7 C-PT12d 0.03 37.2 OIJan2024,13:03 5.72 C-PT12c 0.05 63.83 OIJan2024,13:01 5.69 C-PT12f 0.06 75.33 OIJan2024,13:00 5.7 Contact Ponc 0 4.78 OIJan2024,13:01 6.96 Contact Pond Stomgc 0.09 1.3 OIJan2024,12:12 0.52 Culvert-30inlel 0.11 27.21 OIJan2024,13:01 1.45 Culvert-36in1e1 0.08 87.47 OIJan2024,13:02 5.16 Culvert-60Ialel 0.1 127 OIJan2024,13:02 5.67 Cut Slope 1 0 1 OIJan2024,13:00 5.52 Cut Slope 2 0 1.12 OIJan2024,13:00 5.52 Cut Slope 3 0 0.62 OIJan2024,13:00 5.52 N Nc Swale3 0 4.64 OIJan2024,13:00 6.24 N Ncos8 0.01 10.19 OIJan2024,13:00 6.24 N_C-PTlla 0.03 32.86 OIJan2024,13:00 5.7 N_C-PT1It, 0.01 10.59 OIJan2024,13:00 5.82 N_C-PTllc 0 1.71 OIJan2024,13:00 6.12 N_C-PT12a 0 4.32 OIJan2024,13:00 5.4 N_C-PT126 0.02 26.31 OIJan2024,13:00 5.7 N_C-PT12c 0.03 37.22 OIJan2024,13:00 5.72 N_C-PT12d 0.05 63.87 OIJan2024,13:00 5.69 N_C-PT12c 0.06 75.4 OIJan2024,13:00 5.7 N_C-PT12f 0.07 85.73 OIJan2024,13:00 5.71 N_NC-SWALE4 0 6.49 OIJan2024,13:00 6.24 N_NC-TPad5 0 3.26 OIJan2024,13:00 5.13 N_NC_Pad4 0.01 10.39 OIJan2024,13:00 5.86 N_NC_Swalel 0.01 12.78 OIJan2024,13:00 5.93 N_NC_Swale2 0 1.85 OIJan2024,13:00 6.24 N_TPADI-INLET 0.04 43.3 OIJan2024,13:02 5.06 N_TPAD2-INLET 0.01 7.16 OIJan2024,13:00 5.32 NC-CULV-TPADI 0.04 43.3 OIJan2024,13:03 5.06 NC-CULV-TPAD2 0.01 7.16 OIJan2024,13:01 5.32 Nc Swale2 0 1.86 OIJan2024,13:01 6.24 NC_Pad6 0 3.25 OIJan2024,13:03 5.13 Offsitc-1 0.01 6.16 OIJan2024,13:00 5.28 Offsitc-2 0.01 13.37 OIJan2024,13:03 5.05 Offsitc-3 0.01 12.61 OIJan2024,13:09 5.05 Offsitc-4 0.02 16.61 OIJan2024,13:08 5.05 Offsitc-5 0 2.64 OIJan2024,13:02 5.05 Offsitc-6 0.03 35.98 OIJan2024,13:04 5.05 Offsitc-7 0.01 9.36 OIJan2024,13:00 5.05 Offsitc-8 0.01 8.62 OIJan2024,13:01 5.17 Octfall-60 0.1 128.58 OIJan2024,13:00 5.68 Outfall 30 0.11 28 OIJan2024,13:00 1.48 Outfall 36 0.08 91.56 OIJan2024,13:00 5.16 Pad l 0 3.7 OIJan2024,13:00 6.24 Pad 0 2.78 OIJan2024,13:00 6.24 Pad 3 0 2.38 OIJan2024,13:00 6.24 Pad 0.01 7.15 0IJan2024,13:00 6.24 Pad 5 0 0.93 OIJan2024,13:00 6.24 Pad 0 1.85 0IJan2024,13:00 6.24 Pad? 0 0.93 0IJan2024,13:00 6.24 Perim 1 0.02 22.35 0IJan2024,13:00 5.64 Perim 0.01 8.89 0IJan2024,13:00 5.76 Perim 0 1.71 0IJan2024,13:00 6.12 Perim 0 4.32 OIJan2024,13:00 5.4 Perim 5 0.02 22.04 OIJan2024,13:00 5.76 Perim 0.01 10.98 OIJan2024,13:00 5.76 Perim? 0.02 26.81 OIJan2024,13:00 5.64 Perim 8 0.01 11.61 OIJan2024,13:00 5.76 Perim 0.01 10.4 OIJan2024,13:00 5.76 Perim Culven 0.09 118.59 0 J-2024:13:00 5.7 Perim Sink 0.3 241.63 OIJan2024,13:02 3.93 S Wale 4 0 4.64 OIJan2024,13:01 6.24 Sed Pond 0 1.55 OIJan2024,13:00 7.56 Tsf 0.09 84.19 OIJan2024,13:00 3.64 TSE_Sumf 0.09 1.3 0IJan2024,10:03 0.59 Page 1 of 1 SRK Consulting B.-HBH Warka-Archdale Peron 01APR2024.%Ism 4/3/2024 TABLE B-3d FLOW RESULTS FROM HEC-HMS Albemarle Kings Mountain PFS Archdale Channel Design Date: 4l3/24 PROJECT NO.:USPR000576 By:DPH Chkd: HMS Run Description PMP (Data Range Name:HECHMS_PMP) V Copy entire HTML Output from Standard Report(Global results ONLY)and paste in cell beloo Project:Archdale_Perimeter_Q Simulation Run:Archdale PMP Simulation Start:31 December 2023,24:00 Simulation End:2 January 2024,12:00 HMS Version:4.11 Executed:28 March 2024,22:46 Global Results Summary Hydrologic Element Drainage Area Peak Discharge Time of Peak Volume(IN) (M12) (CFS) Archdale ScdPonc 0.1 687.57 OIJan2024,03:30 25.31 C-PT11A 0.01 60.01 0IJan2024,03:34 25.44 C-PTIIB 0 9.45 0IJan2024,03:35 25.86 C-PT 12b 0 25.16 OIJan2024,03:34 24.85 C-PT12c 0.02 150.69 0IJan2024,03:31 25.28 C-PT 12d 0.03 212.84 OIJan2024,03:32 25.31 C-PT12c 0.05 366.27 OIJan2024,03:30 25.26 C-PT12f 0.06 432.02 OIJan2024,03:30 25.28 Contact Ponc 0 25.12 OIJan2024,03:33 26.93 Contact Pond Storage 0.09 4.41 OIJan2024,06:25 0.95 Culvert-30inlel 0.11 155.03 OIJan2024,03:30 5.52 Culvert-36in1e1 0.08 533.78 OIJan2024,03:30 24.47 Culvert-60Ialel 0.1 739.37 OIJan2024,03:30 25.24 Cut Slope 1 0 5.76 OIJan2024,03:30 25.03 Cut Slope 2 0 6.48 OIJan2024,03:30 25.03 Cut Slope 3 0 3.6 OIJan2024,03:30 25.03 N Nc Swale3 0 25.48 OIJan2024,03:30 26.02 NNcos8 0.01 56.04 OIJan2024,03:30 26.02 N_C-PTI Is 0.03 188.74 OIJan2024,03:30 25.28 N_C-PT]16 0.01 60.02 OIJan2024,03:30 25.45 N_C-PTllc 0 9.45 OIJan2024,03:30 25.87 N_C-PT12a 0 25.18 OIJan2024,03:30 24.86 N_C-PT126 0.02 150.71 OIJan2024,03:30 25.29 N_C-PT12c 0.03 212.86 OIJan2024,03:30 25.31 N_C-PT12d 0.05 366.35 OIJan2024,03:30 25.26 N_C-PT12c 0.06 432.1 OIJan2024,03:30 25.28 N_C-PT12f 0.07 491.24 OIJan2024,03:30 25.29 N_NC-SWALE4 0 35.67 0IJan2024,03:30 26.02 N_NC-TPad5 0 19.72 0IJan2024,03:30 24.44 N_NC_Pad4 0.01 58.98 0IJan2024,03:30 25.48 N_NC_Swalel 0.01 72.08 0IJan2024,03:30 25.58 N_NC_Swale2 0 10.19 OIJan2024,03:30 26.03 N_TPADI-INLET 0.04 252.32 OIJan2024,03:37 24.33 N_TPAD2-INLET 0.01 42.26 OIJan2024,03:30 24.73 NC-CULV-TPADI 0.04 252.32 OIJan2024,03:38 24.33 NC-CULV-TPAD2 0.01 42.24 OIJan2024,03:30 24.72 Nc Swale2 0 10.19 OIJan2024,03:30 26.02 NC_Pad6 0 19.71 OIJan2024,03:32 24.44 Offsitc-1 0.01 36.49 OIJan2024,03:30 24.68 Offsitc-2 0.01 81.26 OIJan2024,03:34 24.31 Offsitc-3 0.01 73.37 0IJan2024,03:44 24.31 Offsitc-4 0.02 97.23 0IJan2024,03:43 24.31 Offsitc-5 0 16.14 0IJan2024,03:32 24.31 Offsitc-6 0.03 217.28 0IJan2024,03:35 24.31 Offsitc-7 0.01 56.82 OIJan2024,03:30 24.31 Offsitc-8 0.01 51.9 OIJan2024,03:30 24.5 Outfall-60 0.1 739.47 OIJan2024,03:30 25.25 Outfall 30 0.11 156.4 OIJan2024,03:30 5.56 Outfall 36 0.08 534.01 OIJan2024,03:30 24.47 Pad 1 0 20.37 0IJan2024,03:30 26.03 Pad 2 0 15.29 0IJan2024,03:30 26.03 Pad 3 0 13.1 0IJan2024,03:30 26.03 Pad 4 0.01 39.31 0IJan2024,03:30 26.03 Pad 5 0 5.1 OIJan2024,03:30 26.03 Pad 6 0 10.19 0IJan2024,03:30 26.03 Pad? 0 5.1 0IJan2024,03:30 26.03 Perim 1 0.02 128.81 0IJan2024,03:30 25.2 Perim 2 0.01 50.58 OIJan2024,03:30 25.37 Perim 3 0 9.45 OIJan2024,03:30 25.87 Perim 4 0 25.18 OIJan2024,03:30 24.86 Perim 5 0.02 125.59 OIJan2024,03:30 25.37 Perim 6 0.01 62.23 OIJan2024,03:30 25.37 Perim 7 0.02 153.67 0IJan2024,03:30 25.2 Perim 8 0.01 65.83 0IJan2024,03:30 25.37 Perim 9 0.01 59.22 0IJan2024,03:30 25.37 Perim_Culven 0.09 679.97 0IJan2024,03:30 25.29 Perim Sink 0.3 1428.18 OIJan2024,03:30 17.54 S Wale 4 0 25.47 OIJan2024,03:30 26.02 Sed Pond 0 7.9 OIJan2024,03:33 27.62 Tsf 0.09 598.96 OIJan2024,03:30 21.81 TSE_Suml 0.09 1.3 OIJan2024,00:35 0.81 Page t of t SRK Consulting B.-HBH-ksheet Archdale Peron 01APR2024.%Ism 4/3/2024 Table B-4a Channel Hydraulic Calculations Albemarle Kings Mountain PFS SS, \� Date: 4/3/24 Archdale Channel Design 0 SSR By:DPH PROJ NO.:USPR000576 BW Chkd: A rvd: Channel Design Geo etry Channel Rou hness Parameters Requires Right Minimum Channel Hydraulic Mannings'n' Mannings'n' HEC HMS Channel Left Side Side Bottom Channel Curvature Jump/Impact Riprap for Capacity for Stability Reach Design Storm Element ID Length Bed Slope Slope Slope Width Depth Radius Block Calc Calculation Design Channel (Depth (Velocity Designation /HMS Run for Q (ft) (ft/ft) (HAV) (H:1 V) (ft) (ft) (ft) (Jump/Block) Methodology Lining Calculation) Calculation) C-PT11a 100 YR N_C-PT11a 2006 0.0043 3.0 3.0 0.0 2.25 0 None G Grass-lined 0.035 0.030 C-PT11b 100 YR N_C-PT11b 1255 0.0524 3.0 3.0 0.0 1.25 0 USACE Steep R Riprap 0.040 0.035 C-PT11c 100 YR N_C-PT11c 555 0.0040 3.0 3.0 0.0 0.75 100 None G Grass-lined 0.035 0.030 C-PT12a 100 YR N_C-PT12a 375 0.0052 3.0 3.0 0.0 1.00 100 None G Grass-lined 0.035 0.030 C-PT-12b 100 YR N_C-PT12b 1807.1 0.0114 3.0 3.0 0.0 1.75 100 None G Grass-lined 0.035 0.030 C-PT12c 100 YR N_C-PT12c 611 0.0085 3.0 3.0 0.0 2.00 100 None G Grass-lined 0.035 0.030 C-PT12d 100 YR N_C-PT12d 1218 0.0102 3.0 3.0 0.0 2.50 100 None G Grass-lined 0.035 0.030 C-PT12e 100 YR N_C-PT12e 532 0.0485 3.0 3.0 0.0 3.00 80 USACE Steep R Riprap 0.040 0.035 C-PT-12f 100 YR N C-PT12f 368 0.0231 3.0 3.0 0.0 3.00 80 USACE Steep R Riprap 0.040 0.035 Page 1 of 3 SRK Consulting BasinH&H W orksheet Archdale Perim 01 APR2024.bsm 4/3/2024 Table B-4a Channel Hydraulic Calculations Albemarle Kings Mountain PFS Date: 4/3/2024 Archdale Channel Design By:DPH PROJ NO.:USPR000576 Chkd: Apprvd: Hydraulic Calculations Channel Evaluations CalculatedHydraulic Maximum Maximum Wave Runup Flow Width Nominal Jump Depth/ Hydraulic Jump Peak Flow Velocity in Normal Flow at Channel Normal Depth Top Width Top Width of at Median Riprap Size Impact Block I Impact Block Reach from HMS Channel Depth Froud Bends Shear Stress t'iAvailable Freeboard of Channel Flow Depth t2lChannel is Dsc Width Length Designation (cfs) (ft/sec) (ft) Number (ft) (lbs/sq ft) (ft) (ft) (ft) (ft) Stable? (in) (ft) (ft) C-PT11a 32.86 3.0 2.0 0.57 0.00 0.5 0.2 13.5 12.1 6.0 Stable C-PT11 b 10.59 5.2 0.9 1.46 0.00 2.8 0.4 7.5 5.2 2.6 See Cale 8 C-PT11c 1.71 1.4 0.7 0.45 0.00 0.2 0.1 4.5 4.0 2.0 Stable C-PT12a 4.32 2.0 0.9 0.54 0.00 0.3 0.1 6.0 5.4 2.7 Stable C-PT-12b 26.31 4.1 1.5 0.88 0.00 1.1 0.2 10.5 9.3 4.6 Stable C-PT12c 37.22 4.0 1.9 0.78 0.00 1.0 0.1 12.0 11.1 5.6 Stable C-PT12d 63.87 5.0 2.2 0.88 0.00 1.4 0.3 15.0 13.2 6.6 Stable C-PT12e 75.40 8.2 1.8 1.60 0.00 5.6 1.2 18.0 11.0 5.5 See Cale 14 C-PT-12f 85.73 6.5 2.2 1.14 0.00 3.2 0.8 18.0 13.3 6.6 See Cale 9 (1)<Vel.Head indicates that the remaining freeboard is less than 1/2 the velocity head(V/2g)suggesting water may splash out. <Oft indicates freeboard is less than recommended value of 0 ft in low flow channel (2)Unstable V indicates that calcuated velocities exceeds the recommended maximum See Calc-refer to appropriate Riprap sizing calculation Page 2 of 3 SRK Consulting BasinH&H W orksheet Archdale Perim 01 APR2024.bsm 4/3/2024 Table B-4a Channel Hydraulic Calculations Albemarle Kings Mountain PFS Date: 4/3/2024 Archdale Channel Design By:DPH PROJ NO.:USPR000576 Chkd: Apprvd: Channel Quantities Channel Surface Channel 13tMinimum (5)Granular Perimeter(per Bank Full Channel Riprap Riprap Filter Reach length) Volume Surface Area Thickness Volume (4)Riprap Filter Thickness Designation (ft) (cy) (ac) (ft) (cy) Material (in) C-PT11a 14.2 30,461 0.66 C-PT11b 7.9 5,883 0.23 1.3 490 Fabric C-PT11c 4.7 937 0.06 C-PT12a 6.3 1,125 0.05 C-PT-12b 11.1 16,603 0.46 C-PT12c 12.6 7,334 0.18 C-PT12d 15.8 22,832 0.44 C-PT12e 19.0 14,352 0.23 2.3 872 Fabric C-PT-12f 19.0 9,928 0.16 1.5 388 Fabric l3)Riprap thickness assumed 2 times riprap D,, tot Granuar filter material beneath riprap recommended when bed slope>10%, filter fabric otherwise (6)Minimum 6"(152 mm)granular filter recommended beneath riprap 9"(228 mm) or greater,4"(102 mm)otherwise. Page 3 of 3 SRK Consulting BasinH&H W orksheet Archdale Perim 01 APR2024.adsm 4/3/2024 Table B-4b Channel Hydraulic Calculations Albemarle Kings Mountain PIPS Road Channel __________________---- Date: 4/3124 Archdale Channel Design 55L 02 IS BY: DPH PROJ NO.:USPR000576 D3 SSR 0.020 1 Chkd: BW ' I Appryd:j Channel Des i n Geometry Channel Roughness Parameters .quires Right Low Flow Minimum Channel Hydraulic Channel n for Road in for Reach Design HEC HMS Channel Lek Slide Side Bottom Channel Channel Curvature Jump/Impact Riprap Capacity Channel n Capacity Road n Designatio Storm I Element ID Length Bed Slope Slope Slope Width Depth Road Width Road Slope Depth Radius Block Cale Calculation Design Channel (Depth (Velocity (Depth (Velocity in HMS Run for 0 (ft) (Wft) (HIV) (H:1V) (R) (R) (ft) (H:M (R) (ft) IJumaelxq Methodology Lining Design Road Material Calculation) Calculation) Calculation) Calculation) C-PT71a PMP N_C-PT1la 2006 0.0043 3.0 3.0 0.0 2.25 60.0 50.0 3.45 0 None G Grass-lined E Earth lined 0.035 0.030 0.025 0.022 C-PT11b PMP N_C-PT11b 1255 0.0524 3.0 3.0 0.0 1.25 60.0 50.0 2.45 0 USACE Steep R Riprap E Earth-lined 0.040 0.035 0.025 0.022 C-PT110 PMP N_C-PT1 to 555 0.0040 3.0 3.0 0.0 0.75 60.0 50.0 1.95 100 None G Grass-lined E Earth-lined 0.035 0.030 0.025 0.022 C-PT12a PMP N_C-PT12a 375 0.0052 3.0 3.0 0.0 1.00 60.0 50.0 2.20 100 None G Grass-lined E Earth-lined 0.035 0.030 0.025 0.022 GPT-12b PMP N_C-PT121, 1807.1 0.0114 3.0 3.0 0.0 1.75 60.0 50.0 2.95 100 None G Grass-lined E Earth-lined 0.035 0.030 0.025 0.022 C-PT12C PMP N_C-PT12c 611 0.0085 3.0 3.0 0.0 2.00 90.0 50.0 3.80 100 None G Grass-lined E Earth-lined 0.035 0.030 0.025 0.022 C-PT12d PMP N_C-PT12d 1218 0.0102 3.0 3.0 0.0 2.50 90.0 50.0 4.30 100 None G Grass-lined E Earth-lined 0.035 0.030 0.025 0.022 C-PT12e PMP N_C-PT12e 532 0.0485 3.0 3.0 0.0 3.00 90.0 50.0 4.80 100 USACE Sleep R Riprap E Earth-lined 0.040 0.035 0.025 0.022 GPT-12f PMP N_C-PT12f 368 0.0231 3.0 3.0 0.0 3.00 130.0 50.0 5.60 100 USACE Sleep R Riprap E Earth-lined 0.040 0.035 0.025 0.022 Page 1 of 3 SRK Consulting BaanHaH WarkaM1eel ArcM1tlale Pent 01-024 - 4/3/2024 Table B-4b Channel Hydraulic Calculations Albemarle Kings Mountain PFS Date: 4/3/2024 Archdale Channel Design By:DPH PROJ NO.: USPR000576 Chkd: A rvd: Hydraulic Calculations Channel Evaluations Top Width Flow Width Calculated Hydraulic Maximum Maximum Maximum Wave Runup Normal Top Width of Flow in Top Width at Median Nominal Jump Depth/ Hydraulic Reach Peak Flow Flow In Velocity In Velocity In Normal Road Freud at Channel Depth Shear of Channel Channel of Flow in Depth in Rlprap Size Impact Block Jump/Impact Designalio from HMS Channel Channel Road Flow Depth Number in Bends Stress (')Available Fmeboard and Road and Road Channel Channel IftChannel is D. Width Block Length n (cfs) (cfs) (ft/sec) (ft/sec) (fill channel (ft) (lbs/sq ft) ft (ft) (ft) (ft) (ft) Stable? (in) (ft) (ft) C-PT71a 188.74 144.52 4.6 2.6 1.019 0.63 0.00 0.3 0.2 73.5 67.5 16.6 8.3 Stable C-PT11b 60.02 58.92 8.1 3.9 0.298 1.64 0.00 1.0 0.9 67.5 23.3 8.4 4.2 See Colo 14 C-PT110 9.45 7.31 2.1 1.2 0.334 0.50 0.00 0.1 0.9 64.5 22.2 5.5 2.8 Stable C-PT128 25.18 18.78 3.0 1.7 0.471 0.60 0.00 0.2 0.7 66.0 31.0 7.4 3.7 Stable GPT-12b 150.71 117.26 6.3 3.6 0.773 0.97 0.00 0.5 0.4 70.5 51.5 12.8 6.4 Stable C-PT120 212.86 155.87 6.1 3.6 0.969 0.86 0.00 0.5 0.8 102.0 63.3 14.9 7.5 Stable C-PT12d 366.35 286.19 7.5 4.3 1.097 0.98 0.00 0.7 0.7 105.0 73.1 18.3 9.1 Stable C-PT12e 432.10 469.37 13.0 4.2 0.428 1.79 0.00 1.3 1.4 108.0 40.7 19.3 9.6 See Calc 32 GPT-12f 491.24 450.34 10.0 5.4 0.867 1.27 0.00 1.3 1.7 148.0 63.9 20.6 10.3 See Colo 20 (1)<Val.Head indicates that the remaining freeboard is less than 112 the velocity head(V/2g)suggesting water may splash out. <oft indicates freeboard is less than recommended value of 0 It M Unstable V indicates that calcuated velocities exceeds the recommended maximum See Calc-refer to appropriate Riprap sizing calculation Page 2 of 3 SRK Consulting BaanH&H W arkaM1eel AmM1tlale Penm 01APR2024.x1am 4/3/2024 Table B-4b Channel Hydraulic Calculations Albemarle Kings Mountain PIPS Date: 4/3/2024 Archdale Channel Design By:DPH PROJ NO.:USPR000576 Chkd,, A rwd: Channel Quantities Low Flow Low Flow Channel Surface Channel Channel 131Minimum 14Grenular Reach Perimeter(per Bank Full Surface Riprap Riprap Filter Designatio length) Volume Area Thickness Volume 141Riprap Filter Thickness n (ft) (cy) (ac) (ft) (cy) Material (in) co T 6.0 71,617 0.28 GPT11b 3.9 22,599 0.11 2.3 423 Fabric C-PT110 2.8 6,331 0.04 C-PT128 3.4 5,445 0.03 GPT-12b 5.0 47,179 0.21 C-PT120 6.1 26,475 0.09 C-PT12d 7.2 67,546 0.20 C-PT12e 8.2 36,741 0.10 5.3 863 Fabric GPT-12f 9.1 34,593 0.08 3.3 412 Fabric lsl Riprap thickness assumed 2 times riprap Dm (4)Grenuar filter material beneath riprap recommended when bed slope>10%, filter fabric otherwise tsl Minimum 6"(152 mm)granular filter recommended beneath riprap 9"(228 mm) or greater,4"(102 mm)otherwise. Page 3 of 3 SRK Consulting BaanH&H wpkaM1eel Am W,Penm 01A-0-A— 4/3/2024 Table B-4c Channel Hydraulic Calculations Albemarle Kings Mountain PFS SSL \ 41 L/sec Date: 4/3/24 Archdale Channel Design D SSR 3526000 By:DPH PROJ NO.:USPR000576 BW Chkd: Apprvd: Channel Design Geo etry Channel Rou hness Parameters Requires Right Minimum Channel Hydraulic Mannings'n' Mannings'n' HEC HMS Channel Left Side Side Bottom Channel Curvature Jump/Impact Riprap for Capacity for Stability Design Storm Element ID Length Bed Slope Slope Slope Width Depth Radius Block Calc Calculation Design Channel (Depth (Velocity Reach Designation /HMS Run for Q (ft) (ft/ft) (HAV) (H:M (ft) (ft) (ft) (Jump/Block) Methodology Lining Calculation) Calculation) NC-AR13a PMP Offsite-1 1836 0.0053 3.0 3.0 4.0 2.50 100 None G Grass-lined 0.035 0.030 NC-PAD1 100_YR Cut Slope 2 622 0.0195 3.0 3.0 0.0 1.50 0 None G Grass-lined 0.035 0.030 NC-PAD2 100 YR Cut Slope 1 680 0.0189 3.0 3.0 0.0 1.50 0 None G Grass-lined 0.035 0.030 NC-PAD3 100 YR Pad 2 465 0.0189 3.0 3.0 0.0 1.75 0 None G Grass-lined 0.035 0.030 NC-PAD4 100 YR Pad 2 240 0.0234 3.0 3.0 0.0 1.75 0 None G Grass-lined 0.035 0.030 NC-PADS 100_YR Cut Slope 3 326 0.0226 3.0 3.0 0.0 1.50 0 None G Grass-lined 0.035 0.030 NC-PAD6 100 YR N_NC_Pad4 586 0.0194 3.0 3.0 5.0 1.50 0 None G Grass-lined 0.035 0.030 NC-PAD7 100 YR Pad 5 287 0.0201 3.0 3.0 5.0 1.25 0 None G Grass-lined 0.035 0.030 NC-PAD8 100 YR Pad 3 251 0.0238 3.0 3.0 5.0 1.25 0 None G Grass-lined 0.035 0.030 NC-SWALEI 100 YR Pad 3 40 0.0238 10.0 10.0 2.0 1.50 0 None G Grass-lined 0.035 0.030 NC-SWALE2 100 YR N_NC_Swale2 180 0.0186 10.0 10.0 2.0 1.25 0 None G Grass-lined 0.035 0.030 NC-SWALE3 100 YR Pad 2 28 0.0234 10.0 10.0 2.0 1.50 0 None G Grass-lined 0.035 0.030 NC-SWALE4 PMP N_NC-SWALE4 391 0.0258 10.0 10.0 2.0 2.00 0 None G Grass-lined 0.035 0.030 NC-SWALES 100 YR Pad 1 403 0.0234 10.0 10.0 2.0 1.50 0 None G Grass-lined 0.035 0.030 NC-DS1 100 YR N_NC_Swalel 45 0.4000 4.0 4.0 5.0 1.50 0 Robinson R Riprap 0.040 0.035 NC-BROW-T14a 100 YR Offsite-2 525 0.0690 3.0 3.0 0.0 2.0 0 None G Grass-lined 0.035 0.030 NC-BROW-T14b 100_YR Offsite-4 620 0.0890 3.0 3.0 0.0 2.00 0 None G Grass-lined 0.035 0.030 NC-BROW-T14c 100 YR Offsite-4 467 0.0613 3.0 3.0 0.0 2.00 0 None G Grass-lined 0.035 0.030 Page 1 of 3 SRK Consulting BasinH&H W orksheet Archdale Perim 01 APR2024.bsm 4/3/2024 Table B-4c Channel Hydraulic Calculations Albemarle Kings Mountain PFS Date: 4/3/2024 Archdale Channel Design By:DPH PROJ NO.:USPR000576 Chkd: Apprvd: Hydraulic Calculations Channel Evaluations Calculated Hydraulic Maximum Maximum Wave Runup Flow Width Nominal Jump Depth/ Hydraulic Jump Peak Flow Velocity in Normal Flow at Channel Normal Depth Top Width Top Width of at Median Riprap Size Impact Block /Impact Block from HMS Channel Depth Froud Bends Shear Stress "'Available Freeboard of Channel Flow Depth 1�1Channel is D, Width Length Reach Designation (cfs) (ft/sec) (ft) Number (ft) (lbs/sq ft) (ft) (ft) (ft) (ft) Stable? (in) (ft) (ft) NC-AR13a 36.49 3.3 1.5 0.62 0.01 0.5 1.0 19.0 12.8 8.4 Stable NC-PAD1 1.12 2.3 0.4 0.93 0.00 0.5 1.1 9.0 2.6 1.3 Stable NC-PAD, 1.00 2.2 0.4 0.91 0.00 0.5 1.1 9.0 2.5 1.2 Stable NC-PAD3 2.78 2.8 0.6 0.97 0.00 0.7 1.1 10.5 3.6 1.8 Stable NC-PAD4 2.78 3.1 0.6 1.07 0.00 0.8 1.2 10.5 3.5 1.7 Stable NC-PADS 0.62 2.1 0.3 0.96 0.00 0.5 1.2 9.0 2.0 1.0 Stable NC-PAD6 10.39 3.6 0.5 1.03 0.00 0.6 1.0 14.0 8.0 6.5 Stable NC-PAD7 0.93 1.6 0.1 0.85 0.00 0.2 1.1 12.5 5.7 5.4 Stable NC-PADS 2.38 2.3 0.2 1.00 0.00 0.3 1.01 12.5 6.2 5.6 Stable NC-SWALEI 2.38 2.2 0.3 0.99 0.00 0.4 1.21 32.0 7.2 4.6 Stable NC-SWALE2 1.85 1.9 0.2 0.87 0.00 0.3 1.01 27.0 6.9 4.5 Stable NC-SWALE3 2.78 2.3 0.3 0.99 0.00 0.4 1.21 32.0 7.6 4.8 Stable NC-SWALE4 35.67 4.6 0.8 1.22 0.00 1.4 1.21 42.0 18.8 10.4 Stable NC-SWALE5 3.70 2.5 0.3 1.01 0.00 0.5 1.21 32.0 8.4 5.2 Stable NC-DS1 12.78 9.2 0.3 3.62 0.00 6.3 1.21 17.0 7.0 6.0 See Calc 9 NC-BROW-T14a 13.37 6.9 0.9 1.95 0.00 3.7 1.11 12.0 5.1 2.6 Stable NC-BROW-T14b 16.61 8.0 0.9 2.23 0.00 4.9 1.11 12.0 5.3 2.7 Stable NC-BROW-T14c 16.61 6.9 0.9 1.87 0.00 3.6 1.11 12.0 5.7 2.8 Stable ('l<Vel.Head indicates that the remaining freeboard is less than 1/2 the velocity head(V/2g)suggesting water may splash out. <1ft indicates freeboard is less than recommended value of 1 ft in low flow channel (2)Unstable V indicates that calcuated velocities exceeds the recommended maximum See Calc-refer to appropriate Riprap sizing calculation Page 2 of 3 SRK Consulting BasinH&H W orksheet Archdale Perim 01 APR2024.bsm 4/3/2024 Table B-4c Channel Hydraulic Calculations Albemarle Kings Mountain PFS Date:1 4/3/2024 Archdale Channel Design By:DPH PROJ NO.:USPR000576 Chkd: rvd: Channel Quantities Channel Surface Channel 131Minimum I51Granular Perimeter(per Bank Full Channel Riprap Riprap Filter length) Volume Surface Area Thickness Volume 14IRiprap Filter Thickness Reach Designation (ft) (cy) (ac) (ft) (cy) Material (in) NC-AR13a 19.8 52,774 0.83 NC-PAD1 9.5 4,199 0.14 NC-PAD, 9.5 4,590 0.15 NC-PAD3 11.1 4,272 0.12 NC-PAD4 11.1 2,205 0.06 NC-PADS 9.5 2,201 0.07 NC-PAD6 14.5 8,351 0.19 NC-PAD7 12.9 3,139 0.09 NC-PADS 12.9 2,745 0.07 NC-SWALEI 32.1 1,020 0.03 NC-SWALE2 27.1 3,263 0.11 NC-SWALE3 32.1 714 0.02 NC-SWALE4 42.2 17,204 0.38 NC-SWALE5 32.1 10,277 0.30 NC-DS1 17.4 743 0.02 1.5 43 Granular 4 NC-BROW-T14a 12.6 6,300 0.15 NC-BROW-T14b 12.6 7,440 0.18 NC-BROW-T14c 12.6 5,604 0.14 (a)Riprap thickness assumed 2 times riprap D50 (4)Granuar filter material beneath riprap recommended when bed slope>10%, filter fabric otherwise 151 Minimum 6"(152 mm)granular filter recommended beneath riprap 9"(228 mm) or greater,4"(102 mm)otherwise. Page 3 of 3 SRK Consulting BasinH&H W orksheet Archdale Perim 01 APR2024.adsm 4/3/2024 Table B-5a U.S. Corps of Engineers (Steep) Method Riprap Size Calculation Albemarle Kings Mountain PFS Date: 4/3/24 Archdale Channel Design By: DPH PROJECT NO.: USPR000576 Chkd: Apprvd: USACE Method for flow in Channel Section Only Riprap Calculations for Steep Riprap Bed Slopes>2%but<20%) Normal Calculated Nominal Design Flow Flow Depth Flow Unit Flow Particle Riprap Riprap Reach Designation Q in Channel d Concentration qt'I Size D30 Size D50 Size D50 (cfs) (ft) Factor (cfs/ft) (ft) (in) (in) C-PT11 b 54.0 1.50 1.25 16.09 0.88 13.8 14 C-PT12e 422.5 3.30 1.25 54.77 1.91 29.8 32 C-PT-12f 415.5 3.75 1.25 50.43 1.20 18.7 20 USACE Paper EM 1110-2-1601,6/30/94 1.95So.55sg2/3 Where: D30=Rock size 30%passing,S=bed slope, D30 gees/3 q=unit flow,gee=gravity Inputs below as determined in EM 1110-2-1601,6/30/94 Unit flow rate is Q/median width,adjusted by a flow concentration factor of 1.25 (USACE steep riprap method recommends a flow concentration factor of 1.25) Riprap D50 determined as recommended in EM 1110-2-1601,6/30/94 (D85\1/3 Where: Dx=rock size X%passing, Dso =D30 /I D15 2.2 Cg: Gradation Coefficient(45015) Page 1 of 1 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xlsm 4/3/2024 Table B-5b Robinson Method Riprap Size Calculation Albemarle Kings Mountain PFS Date:1 4/3/24 Archdale Channel Design By: DPH PROJECT NO.: USPR000576 Chkd: Apprvd: Robinson Design of Rock Chutes Riprap Calculations for Steep Riprap(Bed Slopes>2%but<40%) Calculated Particle Size Calculated Nominal Design Flow Unit Width D50 Riprap Size Riprap Flow Q Concentration Flow q (2) Factor of D50 Size D50 Reach Designation (cros) Factor (cros/m) (mm) Safety (in) (in) NC-DS1 0.362 1.25 0.247 178 1.20 8.43 9 Design of Rock Chutes(ASAE Paper No.982136 7/98) Determine unit flow at incipient motion for rock particle size Unit flow rate is Q/median width,adjusted by a flow concentration factor of 1.25 (USAGE steep riprap method recommends a factor of 1.25) (2)Bed Slope<10%: q =9.76x10-7D501.895-1.50 10%<=Bed Slope—40%: q=8.07x10-6D501'89S-0.58 1.2 Factor of Safety over incipient motion Page 1 of 1 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xlsm 4/3/2024 Table B-6 Sediment Pond Sizing Calculation Albemarle Kings Mountain PFS Date: 4/3/24 Archdale Channel Design By: DPH PROJECT NO.:USPR000576 Chkd: A rvd: Design Criteria,NDEQ Erosion Control Design Manual Practice Standard 6.61-Sediment Basin Design Criteria Summary: Primary Spillway:Riser/Barrel Pipe Maximum Drainage Area: 100 ac Minimum Sediment Storage Volume: 1800 ft3/ac of disturbed area Minimum Surface Area: 435 ft2/cfs of Q10 peak inflow Minimum L/W Ratio: 2:1 Maximum L/W Ratio: 6:1 Minimum Depth: 2 ft Dewatering Mechanism: Skimmer(s)attached at bottom of riser pipe or flashboard riser Minimum Dewatering Time: 48 hrs Baffles Required: 3 baffles (*Note:Basins less than 20 feet in length may use 2 baffles.) Sediment Basin T-A-Archdale Sediment Pond,Basins Perim 1-12 Contributing Watershed 64.00 acres Check Perim_Culvert 10_YR Peak flow to Sediment Pond 619 0 cfs Perim_Culvert 100_YR Peak Channel Design Flow 118.59 Is Peak Spillway inflow 1400 gpm 3.12 cfs Design Pond Capacity to Spillway: 115,200 ft3 2.64 ac-ft Surface Area to Spillway: 30,276 sq ft 0.695 acres To Dimensions Pond Top Length 500 ft Pond Bottom Width 90 ft Pond Depth to Crest 12 ft PMP Height to Spillway 5.5 ft Pond Side Slopes 2 AV L/W Ratio 5.6 Check Pond Length at Spillway 474 Time to Drain 2.64 ac-ft pond with 8 in Skimmer Float with 6 in Pond Width at Spillway 64 Orifice Pond Top Area at Spillway 0.696 acres Check 6 0.9 Pond Bottom Length 452 ft Pond Bottom Width 42 ft o.s s Pond Bottom Area 0.44 acres 0.7 Pond Volume at Spillway 3.11 ac-ft Check 7 w 4 0.6 0.291666667 Rymar Mai ee Float Size 8 in o 0.267253542 Rymar Madee Orifice Size 6 in a o.s Initial Depth in Pond 5.5 ft ` 3 t o.a 0 v Dewatered when Depth<= 0.1 ft g £ Peak Outflow 0.854 cfs o 2 0.3 383 gpm ^ Time to Dewater 51.0 hrs Check 0.2 1 0.1 PMP Spillway Width 14 ft o 0.0 PMP Spillway Side Slopes 3 HAV o 10 20 30 40 so 60 70 Weir Coefficient 3.09 Elapsed Time(hours) Peak Head in Spillway 2.5 ft Peak Inflow to Pond 3.1 —Depth in Pond —Skimmer Outflow Peak Outflow from Spillway 244.3 cfs Check Freeboard in Spillway 4.00 ft Page 1 of 1 SRK Consulting BasinH&H Worksheet Archdale Perim 01 APR2024.xism 4/3/2024 Attachment B-1 Time of Concentration and Mannings Flow Coefficients NEH4-Chapter 15(Time of Concentration)2010 Sheet Flow Travel time(mannings's kinematic solution) 0.007(n'L)°$ Where: Tt=travel time(hr);n'=roughness coefficient;L=flow length(ft); Tt= (p2)0.SSo.4 P2=2-yr storm depth(inches);s=slope(ft/ft) flow velocity=L/(60Tt) Short Flow Type Surface Type roughness n Surface Description Description A 0.011 Smooth surfaces(concrete,asphalt,gravel,bare soil) Smooth 3 B 0.05 Fallow(no residue) Fallow 0 LL C 0.06 Cultivated soils:Residue cover—20% Cover<20% = D 0.17 Cultivated soils:Residue cover>20% Cover>20% `2 E 0.15 Grass: Short grass prairie Short Grass > F 0.24 Grass: Dense grasses Dense Grass o G 0.41 Grass: Bermuda grass Bermuda Grass H 0.13 Range(natural) Range y 1 0.40 Woods: Light underbrush Light woods J 0.80 Woods:Heavy underbrush Heavy Woods Shallow Concentrated Flow Velocity v=mS Where: v=velocity(fps);m=roughness coeffient;S=slope Short Flow Type Surface Type Roughness m Surface Description Description P 20.3282 Pavement and small upland gullies Paved 3 G 16.135 Grassed waterways Grass 0 Nearly bare and untilled(overland flow);and alluvial fans ILL 6 B 9.965 in western mountain regions Bare c 0 v C 7.762 Cultivated straight row crops Crops 3 0 s S 6.962 Short-grass pasture Short-grass y Minimum tillage cultivation,contour or strip-cropped,and W 5.032 woodlands Woodlands F 2.516 Forest with heavy ground litter and hay meadows Forest Channel Flow Velocity(Mannings Velocity) Where: v=velocity(mps);n=roughness coeffient;Rh=Hydraulic Radius(m),S v=Ct/n Rh2 3S12 =slope(m/m),Cf=Imperial/Metric conversion factor Maximum Conduit Mannings n Mannings n Velocity Type for Depth for Velocity Material (ft/sec) A 0.026 0.026 ACB 25.00 C 0.024 0.022 CSP 50.00 E 0.025 0.022 Earth-lined 5.00 G 0.035 0.030 Grass-lined 8.00 1 0.017 0.013 Ductile Iron 50.00 P 0.014 0.012 Plastic 25.00 R 0.040 0.035 Riprap T 0.035 0.030 Turf Reinf. 10.00 Z 0.015 0.015 lConcrete 60.00 Page 1 of 1 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xism 4/3/2024 Attachment B-2 Riprap Gradation Table USACE HYDRAULIC DESIGN OF FLOOD CONTROL CHANNELS Extrapolated from Table 3.1 Gradations for Riprap Placement in the Dry,Low-Turbulence Zones EM 1110-2-1601 6/30/1994 Nominal Percent Riprap Gradation Requirements Riprap Less than Acceptable Range of Size (by Particle Size (D50) Weight) (in) 100 Min Max 100 6.7 to 9.0 90 90 6.4 6 in 50 5.2 to 6.0 30 4.4 80 15 3.4 to 4.6 100 10.0 to 13.5 70 90 9.5 9 in 50 7.9 to 9.0 60 30 6.5 L 15 5.3 to 7.2 ~ ffi W 50 100 11.0 to 15.0 90 10.6 2 10 in 50 8.8 to 10.0 a" 40 30 7.3 15 6.0 to 7.9 30 100 13.3 to 18.0 -6 in 90 12.7 20 12 in 50 10.5 to 12.0 - in 30 8.8 -10 in 15 7.1 to 9.5 10 -12 in -18 in 100 19.9 to 27.0 90 19.1 0 18 in 50 15.8 to 18.0 0 6 z s 24 30 30 13.2 Particle Size(inches) 15 10.7 to 14.3 Based on a Specific Gravity of rock of 165 pcf Page 1 of 1 SRK Consulting BasinH&H Worksheet Archdale Perim 01APR2024.xism 4/3/2024 SRK Consulting(U.S.), Inc. Surface Water Management Report—Kings Mountain Appendices Appendix D-3: Erosion and Sediment Control Plan DH/MH Archdale_StormwaterManagement_TR_USPR000576_Rev02.docx April 2024 Archdale Development and Operational Erosion and Sediment Control Plan Kings Mountain Mining Project Report Date: April 4, 2024 Report Prepared for A ALBEMARLE' Albemarle Corporation 4250 Congress Street Charlotte, NC 28209 Report Prepared by srk consulting SRK Consulting (U.S.), Inc. 999 171h Street, Suite 400 Denver, CO 80202 SRK Project Number: USPR000576 Albemarle Document Number: KM60-EN-RP-9052 North Carolina Firm License Number: C-5030 Author: Mauricio Herrera, PhD, P.Eng., Principal Consultant Reviewed by: David Hoekstra, BS, PE, NCEES, SME-RM, Principal Consultant SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page ii Executive Summary SRK Consulting (U.S.), Inc. (SRK) has developed an erosion and sediment control plan (ECP)for the Archdale tailings storage facility (TSF) component of the Kings Mountain Mining Project (the Project) has been developed in support of the prefeasibility study (PFS) environmental assessment (EA) application. The ECP was prepared for the proposed life-of-mine (LoM), including construction, operation, and concurrent reclamation. A separate ECP will be prepared to address the closure, decommissioning, and reclamation of the facility. Design criteria have been selected based on applicable regulations and associated guidance documents, including the North Carolina Surface Mining Manual (1996), the Global Industry Standard on Tailings Management (GISTM) (2020) Flood Design Criteria, and with consideration for Project-specific risks. The objective of the ECP is to provide a strategy for specific Project locations that require controls to reduce the amount of erosion and sedimentation that can occur because of the Project. Design criteria for the Project have been selected to meet or exceed the requirements of the North Carolina Surface Mining Manual (1996) and the North Carolina Erosion and Sediment Control Planning and Design Manual (NCSCC) (2013). Table 1 shows the selected criteria and the North Carolina recommendations. Table 1: Surface Water Design Criteria Infrastructure Project Design Criteria Recommended by North Carolina Type Mining Manual 1996 and NCSCC Permanent channels Probable maximum precipitation 10-year storm (temporary) adjacent to the TSF PMP local storm 25-year storm permanent Permanent channels in 100-year storm 10-year storm (temporary) the non-process area 25- ear storm (permanent) Culverts PMP local storm 25-year storm 25-year storm for all sediment control ponds 0 10-year storm (less than (<)20 acres(ac)) Ponds 100 percent(/o)containment of 25-year storm (greater than (>)20 ac) the PMP storm event for TSF collection pond Permanent Probable maximum flood (PMF) 10-year storm (temporary) channels 25-year storm (permanent) Culverts PMF 25-year storm Ponds 25-year storm for all ponds 10- ear storm <20 ac 25- ear storm >20 ac Non-contact perimeter channels are designed to route runoff from undisturbed areas around Project infrastructure into Archdale Creek, maintaining clean water. Erosion protection for channels was selected based on the maximum tributary catchment throughout the life of the Project and the expected velocities during design flood events. Most of the channels are grass-lined, while those segments with steeper gradient are lined with riprap. One sediment control pond will be situated downstream of the TSF perimeter channels to manage non-contact water from the active TSF perimeter corridor before discharging into Archdale Creek. Non- contact water collected from areas in the non-process infrastructure components of the Archdale site will be revegetated or resurfaced during the initial development stage and will only require sediment controls during the facility construction. Once the surfaces have stabilized, non-contact water from these areas will be conveyed through the Project site and released to Archdale Creek without additional sediment requirement. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page iii Table of Contents ExecutiveSummary.......................................................................................................... ii 1 Project Description...................................................................................................... 1 1.1 Site Description...................................................................................................................................1 1.2 Property Location................................................................................................................................3 1.3 Property History ..................................................................................................................................3 1.4 Project Overview.................................................................................................................................4 1.4.1 Project Layout .........................................................................................................................4 2 Erosion and Sediment Controls ................................................................................. 6 2.1 Design Objectives...............................................................................................................................6 2.2 Design Criteria ....................................................................................................................................6 2.2.1 North Carolina Surface Mining Manual (1996)........................................................................6 2.2.2 Project-Adopted Criteria..........................................................................................................7 2.3 Methodology........................................................................................................................................7 3 Erosion and Sediment Controls ................................................................................. 8 4 Construction Schedule.............................................................................................. 10 4.1 Phase 1: Site Preparation.................................................................................................................10 4.1.1 Topsoil Salvage and Unsuitable Soil Removal .....................................................................10 4.2 Phase 2: Facility Construction ..........................................................................................................10 4.2.1 Perimeter Access Road and Starter Embankment Construction..........................................10 4.2.2 TSF Interior Base and Side Slope Design ............................................................................11 4.3 Phase 3: Operations .........................................................................................................................11 4.3.1 Raise Construction................................................................................................................11 4.3.2 Tailings Placement and Tailings Surface Management........................................................11 4.3.3 Stormwater Management......................................................................................................12 4.4 Phase 4: Closure...............................................................................................................................12 5 Planned Erosion and Sedimentation Control Practices ......................................... 13 5.1 Permanent Development- and Operational-Stage Practices............................................................13 5.1.1 Permanent Sediment Control Pond ......................................................................................13 5.1.2 Sediment Fence (Practice 6.62)............................................................................................14 5.1.3 Permanent Grass-Lined Channels (Practice 6.21 and Practice 6.30)..................................14 5.1.4 Permanent Riprap-Lined Channels (Practice 6.21 and Practice 6.31).................................15 5.1.5 Permanent Outlet Protection Level Spreader (Practice 6.40)...............................................15 5.1.6 Operational Dust Control (Practice 6.84)..............................................................................15 5.1.7 Operational Temporary Seeding (Practice 6.10) ..................................................................15 5.2 Closure Stage Practices ...................................................................................................................15 MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page iv 5.3 Temporary Development Stage Practices........................................................................................15 5.3.1 Temporary Dust Control (Practice 6.84) ...............................................................................16 5.3.2 Temporary Sediment Traps (Practice 6.60)..........................................................................16 5.3.3 Sediment Fence (Practice 6.62)............................................................................................16 6 Maintenance Plan....................................................................................................... 17 7 Detail Drawings and Specifications for Practices Specified.................................. 19 8 Vegetation Plan.......................................................................................................... 24 9 Supporting Calculations............................................................................................ 25 10 Financial Responsibility/Ownership Form............................................................... 26 11 Checklist..................................................................................................................... 27 12 References.................................................................................................................. 28 Disclaimer........................................................................................................................ 29 Copyright ......................................................................................................................... 29 List of Tables Table 1: Surface Water Design Criteria.............................................................................................................. ii Table 2.1: Project Design Criteria for Surface Water Infrastructure...................................................................7 Table 5.1: TSF Sediment Pond Volume and Surface Areas............................................................................14 Table 8.1: Preliminary Seed Mix Composition and Schedule ..........................................................................24 List of Figures Figure1.1: Location Map....................................................................................................................................2 Figure 1.2: Preliminary Kings Mountain Mining Project Archdale Site Map.......................................................4 Figure 3.1: Archdale Erosion and Sediment Control Plan..................................................................................9 Figure 7.1: Skimmer and Riser Sediment Basin with Permanent Wet Pond ...................................................19 Figure7.2: Rock Check Dam............................................................................................................................20 Figure 7.3: Typical Riprap Channel Cross-Section ..........................................................................................21 Figure 7.4: Outlet Stabilization Structure..........................................................................................................22 Figure 7.5: Typical Operational Paved Flume..................................................................................................23 MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page v List of Abbreviations The US System for weights and units has been used throughout this report. Tons are reported in short tons of 2,000 lbs. All currency is in U.S. dollars (US$) unless otherwise stated. Abbreviation Unit or Term percent < less than > greater than ac acre Albemarle Albemarle Corporation amsl above mean sea level cfs cubic feet per second CWP contact water pond EA environmental assessment ECP erosion and sediment control plan ESRI Environmental Systems Research Institute, Inc. Foote Foote Mineral Company ft foot ft2 s uare foot ft3 cubic foot GISTM Global Industry Standard on Tailings Management pm gallons per minute 1-85 Interstate 85 LoM life-of-mine MSHA Mine Safety and Health Administration NCSCC North Carolina Erosion and Sediment Control Planning and Design Manual NPI non-process infrastructure PFS prefeasibility stud PMF probable maximum flood PMP probable maximum precipitation Project Kings Mountain Mining Project SRK SRK Consulting (U.S.), Inc. SWCA SWCA Environmental Consultants TSF I tailings storage facility MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 1 1 Project Description The Project is a legacy open pit lithium mining operation located in the city of Kings Mountain, North Carolina, in the southeastern United States. The Project is a lithium pegmatite deposit that is currently being investigated for redevelopment by Albemarle Corporation (Albemarle)as part of a prefeasibility- level analysis. Albemarle commissioned SRK to develop prefeasibility-level (evaluate and select phases, per Albemarle's internal conventions)designs for an expansion of the existing pit, waste rock management, water management, and ancillary infrastructure to aid Albemarle in making informed decisions concerning advancement of the Project. As part of this study, SRK is developing a PFS surface water design of stormwater management controls to divert clean, non-contact water around the facilities.At the same time,the design intercepts waters that have come into contact with mining activities and routes them to monitoring or treatment facilities prior to discharge into the existing natural drainage system. This document provides a detailed ECP for the Archdale TSF. 1.1 Site Description Situated in Cleveland County, the mine is approximately 35 miles west of Charlotte, North Carolina. Located amidst rolling hills of the Piedmont Plateau, the Project is in a predominantly rural setting within the city of Kings Mountain. The mine site covers a significant land area, which includes both the proposed extraction areas and associated processing infrastructure. Figure 1.1 shows the location of the Archdale TSF. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 2 Galax 1 11 91ue Ridge P:ikway 1 � r25I Statesville Asheville 5au[h Ma4■esuille Mounui ns Gi81,e Land LaU North Cafdlina ri sa Green River —` Shelby !;a-io I.nnr1 [ia5[d11id 4 Charlotte Iryr Spartanburg Wadewampmn �RgCkHIM ❑ GreerMlle yet South Carolina Mies Source: Environmental Systems Research Institute, Inc. (ESRI),2023(modified by SRK) Figure 1.1: Location Map As part of this study, SRK is developing a PFS surface water design of stormwater management channels, detention and retention ponds, sediment control structures, and spillways that meet the required design criteria for each facility, which were selected using a risk-based approach. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 3 Incorporated within the surface water design for the Project, SRK developed the ECP for the development and operational stage of the Project. These phases cover the period from the initial site development to the end of mining and start of the closure and reclamation of the Project site. The ECP was developed according to the NCSCC(2013), isolating non-contact runoff from the contact water produced during mining and detailing the non-contact runoff in one of three sediment control structures. 1.2 Property Location Situated in Cleveland County, the mine is approximately 35 miles west of Charlotte, North Carolina. Located amidst rolling hills of the Piedmont Plateau, the Project is in a predominantly rural setting within the city of Kings Mountain. The mine site covers a significant land area, which includes both the proposed extraction areas and associated processing infrastructure. Figure 1.1 shows the location of the mine and the location of the Archdale TSF. 1.3 Property History The following summary highlights the history of the site, compiled from records available to SRK: • Mining started in 1883 with the discovery of cassiterite, a tin-bearing mineral, within the outcropping pegmatites. • Subsequently, open pit mining for tin occurred sporadically between 1903 and 1937 (Horton and Butler, 1988). • Between 1943 and 1945, under the sponsorship of the U.S. government, Solvay established a processing plant and mined for spodumene from the outcropping pegmatites(Garrett,2004). • In the early 1950s, Foote Mineral Company (Foote), a subsidiary of Newmont Mining Corporation, purchased the property and began open pit mining (assumed at the beginning of 1955) and extracting lithium from the spodumene. • In 1993, exploration and mining operations ceased when the open pit bottom reached approximately 660 feet(ft) above mean sea level (amsl). • In early 1994, an open pit lake started to form due to rebounding groundwater, and the pit lake reached an elevation of 818.67 ft amsl (as of November 2023). • During the groundwater recovery period (1994 to present), water was sporadically pumped from the Kings Mountain pit lake to a nearby quarry (Martin Marietta) to support quarry operation. • Albemarle acquired the site in 2015, resuming exploration and mine development activities. The proposed Archdale TSF will be located at the site of a former mica mine. The following summary of the site is compiled from records available to SRK: • The site was formerly owned by the Kings Mountain Mica Company, which began operation in 1949. • The site was owned by several different companies between 1994 and 2021, including Franklin Minerals, Oglebay Norton, Zemex, General Chemical, and Imerys. • Imerys expanded mining to the property north of the Archdale site across Highway 29 in 2011. • Albemarle acquired the site in 2023 for use as a permanent storage of filtered tailings from the Project. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 4 Available aerial photography of the site suggests that mining activities continued through about 2013. The current site layout encompasses several shallow in-pit ponds formed during the previous mica mining operations. Figure 1.2 shows a detailed map of the current site layout. GFTE ENTRANCE -- - -- FEET IMFT.PERIMETER HIGH POINT HAULI ACCESS ROAD l FILTERED % TAILING_ STOR..GE LIGHT VEH[CLE ENTRANCE / / CRE`L FILL T 960 ElFAN nss1 SEEPAGE INTERCEPTI DRAIN PERIMETER ACCESS ROA➢ WATERAN❑SEWER MAIN �1 LIGHTVEHICLE ACCESS ROAD EXISTING CULVERTS(TYP.) PROPOSED CUL`,'ERT;TYP / SEDIMENT BASINS FUEL PAD MAINTENANCE SHOP �(�,� / SEEPAGE COLLECTION TANK CULVERT ABLE TO PASS PUP PROPERTY BOUNDARYOVERHE4D POW ER TON ACT WATER POND GROWN-I MEDIA STOCKPILE(-200k LAY DOWN AREA / TRIJ-PARKING PARKING Source:SRK 2023 Figure 1.2: Preliminary Kings Mountain Mining Project Archdale Site Map 1.4 Project Overview Tailings from the spodumene concentrate process at the Project will be filtered to approximately 10% to 15% moisture content by weight and transported off-site to the proposed Archdale TSF for disposal. A portion of the waste rock mined at the Project will be transported to Archdale for construction of the TSF embankment. An initial TSF embankment will be constructed on-site to hold approximately 1 to 2 years of filtered tailings. Thereafter, filtered tailings material will be placed and compacted with mobile equipment at the same time the TSF perimeter embankment is raised with compacted waste rock and/or fill. The TSF will be constructed in this manner until the facility reaches its capacity, at which time the facility will be closed and reclaimed. 1.4.1 Project Layout Figure 1.2 shows the Project layout and the relative locations of the major components of the Project. The Project is bounded by Interstate 85 (1-85) on the south and Highway 29 on the north. Access to the TSF will be from Highway 29 with separate truck and light vehicle entrances. The proposed MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 5 Archdale site will include a small office and maintenance facilities, parking,water storage and sediment control facilities as part of the non-process infrastructure (NPI), and a TSF perimeter access road. Spaces for a small road base stockpile and a growth media storage area are included in the site plan. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 6 2 Erosion and Sediment Controls 2.1 Design Objectives The objective of the ECP is to provide a strategy for specific Project locations that require controls to reduce the amount of erosion and sedimentation that can occur because of the Project. 2.2 Design Criteria The following standards and guidelines apply with respect to surface water controls: • Surface Mining Manual. A Guide for Permitting, Operation, and Reclamation. State of North Carolina Department of Environment, Health, and Natural Resources. Division of Land Resources. Land Quality Section. February 1996. • Erosion and Sediment Control Planning and Design Manual. North Carolina. May 2013. North Carolina Sedimentation Control Commission, North Carolina Department of Environment and Natural Reserves, and the North Carolina Agricultural Extension Services. • GISTM 2020 Flood Design Criteria. 2.2.1 North Carolina Surface Mining Manual (1996) The North Carolina Surface Mining Manual (1996) stipulates that: • Temporary diversions(those that function for<1 year)should be designed to carry at least the 10-year design storm for the total drainage area; furthermore: o Temporary diversions require erosion protection. Velocities over 2.5 ft per second may require a temporary liner with supporting design calculations unless the soil is especially erosion resistant. o Side slopes of the diversion berm should be constructed to a 2 horizontal to 1 vertical or flatter. The slopes should then be immediately seeded. o Permanent ditches and channels (those constructed to function for more than 1 year and to carry concentrated runoff non-erosively to a predetermined destination) must be designed for the 25-year storm event for the total drainage area; furthermore: o Side slopes must be 2 horizontal to 1 vertical or flatter. o Grass-lined channels are generally used for slopes <5%. o Velocities should not exceed 5 ft per second for established grass-lined channels. o Sharp bends and turns should be avoided. o Velocities over the maximum allowable design velocity for grass-lined channels require a permanent structural lining, such as riprap. o In cases where velocity allows, riprap may be installed in the bottom of the channel with grass-lined side slopes to decrease the quantity of riprap needed. Filter fabric or a 6-inch deep sand gravel crushed stone filter must be installed under the riprap to prevent undermining. The filter should extend under the entire area of the riprap lining. o The receiving channel or outlet must be protected from erosion by ensuring that the outlet velocity is minimized. o Outlet protection should be included if necessary. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 7 o Channels must be stabilized as soon as possible after construction, and sediment-laden runoff must be diverted away from stabilized channels. o Channels must be inspected after every major rainfall and appropriately repaired. 2.2.2 Project-Adopted Criteria Table 2.1 shows project-adopted criteria for the surface water infrastructure (channels, culverts, and sediment ponds)that generally exceeded the North Carolina Mining Manual's recommendations. Table 2.1: Project Design Criteria for Surface Water Infrastructure Infrastructure Project Design Criteria Recommended by North Carolina Type Mining Manual 1996 and NCSCC Permanent channels PMP local storm 10-year storm (temporary) adjacent to the TSF 25- ear storm (permanent) Permanent channels in 100-year storm 10-year storm (temporary) the non-process area 25- ear storm (permanent) Culverts PMP local storm 25-year storm 25-year storm for all sediment control ponds Ponds 100%containment of the PMP storm event 10-year storm ( 20 ac) for TSF collection and 25-year storm (>20 ac) Source:SRK,2023 2.3 Methodology SRK incorporated a stormwater management approach of using runoff treatment; all disturbed areas are managed by sediment control measures, consisting of sediment mitigation at the source and wet ponds or stormwater wetlands to manage discharges to the existing drainages. SRK conducted hydrologic and hydraulic modeling for sizing the channels, determining the erosion protection required, and for sizing the sediment control pond. A description of the methodology is presented in the main report to which this document is an appendix (Archdale Surface Management Report(SRK, 2024)). Appendix B of the main report includes a summary of the calculations. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 8 3 Erosion and Sediment Controls The Preliminary Archdale Tailings Storage Facility Design Drawing Package (SRK, 2024a) presents the TSF's detailed perimeter sections, profiles, and plans. Figure 3.1 shows the channel layout that will be constructed to provide surface water management control during operations, as well as the sediment and erosion controls, including the following: • Sediment pond control with skimmer • Culvert outlet stabilization • Permanent grass-lined channels • Permanent riprap-lined channels • Temporary silt fences • Level spreaders • Rock check dams The channels were sized to safely convey the peak flow produced by the design storm event using the maximum catchments that will contribute to them during the operational period. Channels will be reconfigured during the closure period to address post-closure flows, as described in the separately provided closure plan report (SRK, 2024b). MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 9 UGHT4F}11CLE AND HAUL 1 .In..�..».r __-__ LEGEND • �� VEHICLE SEPARATION BERM � � - _ - wx,ttnxs I�usnYCl •rl '^' 'r' Iw T.FERIMET HAUL/ACCESS ROAk - wnxntinuTsvccl¢p r 'IF LIGHT VEHICLE ACCESS WATER A146SEWER MAIN ---_ '`_ ROCK CHECK DAM SIT€ENTRANCE .uir>F wxTCE �F RFVEGETATFI} y -, L C,CVYSTRI K:TION OUT SLOPE _ _ _ ane�nerr.nc� - - - rxu t _� +� —_ly f GRAVEL T '" x rvncnux� 1` ] i,I Ii� ti.4'ti ',I =4114 TRAFFIC SURFACE , u•c�•_ k t 'r�y �.f F. Ir �'f- i C� pA 111f.!PM FdPMfi PERLMAHENT SELV EH'r { .v PERMANENT RIFRAp A 'I. } +4I7f�I I III CONTROI POND WITH......... _ l r LINED CHANNEL l S _ luven-rruvlel: ~. ~ -- 1'"-� } ii�` - ` PERMANENT GRASS iAUlYF S,�W FPIIr]Pf1M1ll ROCKCHCCFCiQN.I - 7 � �,,... V��- } '-ro�Sy Ali, S UNEDGHAMNEL 4 Xj, �- wxix wr.S�x�Eo LEVELSPREADER _ _ �r 5 _ "h_h,_i°*_ - _ '_ I�• may_ L. — __-`I 1 ' _= :57 *y 1� - —� �lll•tflx Gx:.VIRIWYr11JlL LINEo CHANNEL a PROPERTY BOUNDARY INTERIOR WASTE ROCK _ l ' ; PERIMETER BERM 4 Ylr( .YRf w � �N;`,•`- LE ELSPRCADCR `I - "� z_ I''�, ':- ! r+�/ J `�• CULVERT OUTLET _ - __ ^•'sr o' _ _. �{ ��. ��_�� - :::� �'I: �. .�\ � t+'. STABILEATIO4 - �, * {"' f �� t S-' ,�•. . R PERFA+SNENi RIPR:SP c AR - 3 LINED CF WJNEL i TEMPORARY 9ILT - - — — _ --- _�--�_ FENCE CULVERT OUTLET RE1'EGETATEQ $TA,OILIZATI W -- s —�- ,.., ..�. I — CONSTRUCTION — TEMPORARYSILT F ILL SLOPE FENCE CULVERTOUTLE - r � TJ PERMAWENTSEDIMENT L PMP EMERGENCY OONTRDL POLO WITH SIUMMER SPILLWAY ISTING CULVERTS{TYP.I PFRINFi Ad:CFSS ROAD - STAEl1UZATION AND STARTT ER Eh16AMKhE11T y� CONSTRUCTION EROSION CONTROL PLAN PERIk1EFERACCE38 ROAD HIGH POINT ter�ie.r-aa}I FElINL114 K44r 8rw AI��nG}A PIDYIaEr LNTIS TRf nor ocscrsnul ats u....,a`.. .ua xb 9 consulting DRAFT 3.ONTICLIV9RIlRRlRl1' o-uo� .______.—. LOCATION 4F EROSION CONTROLS Ui.012U2i f I KIWI&MOfTAIN WNE � PRELIM NARY ARCHDALE USPR[•]a5M„'w rA UI 4w{, EROSION AND SEDIMENT CQNTROL PLAN omexm.iwwcllroa KING$MOUNTAIN MINE PROJECT FIGURE C-2 FlE-E VEnaMM10 par v rt.r Rdino{W.�� ,we oovme sax.[lo-xmm Source:SRK,2024 Figure 3.1: Archdale Erosion and Sediment Control Plan MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 10 4 Construction Schedule The following sections describe the conceptual construction schedule of the filtered TSF and associated facilities, the operational period of TSF raise construction, and tailings placement within the facility. 4.1 Phase 1 : Site Preparation 4.1.1 Topsoil Salvage and Unsuitable Soil Removal Prior to construction, the access roads, footprint of the TSF, and plant site will be cleared and grubbed of existing vegetation. Organic topsoil and growth media will be stripped and hauled to a designated stockpile, where it will be stored for reuse during the Project closure phase. Unsuitable soils across the site will be removed and hauled to a designated stockpile, where it will also be stored for reuse during facility closure. 4.2 Phase 2: Facility Construction 4.2.1 Perimeter Access Road and Starter Embankment Construction Initial construction of the TSF will include a perimeter access road constructed around the edge of the existing pit, grading for the NPI pad, and a starter embankment completely within the base of the existing pit. Removal of existing unsuitable material in the future embankment and storage area will be completed concurrently with establishment of the base area for the perimeter road, starter embankment, and filtered tailings storage area. Drainage will be established in the interior of the TSF area. Grading for the NPI pad will include 2.5H:1 cut-and-fill side slopes and nominal 2% pad area. The embankment will be constructed with 1.5H:1 V interior side slopes and 2.5H:1 V exterior side slopes. Excavation cut-and-fills for the NPI pad and perimeter access road will be graded and revegetated during the construction phase.The surface of the NPI pad will incorporate a gravel traffic surface,while the perimeter access road will utilize a compacted road base surface. Construction of the contact water pond (CWP) will take advantage of existing topography, with the construction of the pond primarily in cut with a crest width of 25 ft. The pond will be about 15 ft deep with 2.5H:1V side slopes and constructed without a base liner to facilitate periodic sediment cleanout. Construction of the sediment pond will be incorporated in the perimeter corridor berm construction, in the southwest corner of the TSF perimeter to take advantage of an existing 60-inch culvert discharging under 1-85. Waste rock haul for embankment construction will be via over-the-highway haul trucks from the Kings Mountain mine pit about 3 miles northeast of the TSF. Only non-potentially acid generating waste rock will be used for embankment construction. Temporary haul roads will be constructed as necessary within the pit and tailings placement areas to ensure all-weather access for highway and site haul trucks during operations. Tailings haul trucks will access the interior of the TSF via temporary haul roads constructed off of the main site haul road around the southwest corner of the TSF. Grading of the waste rock embankment and subgrade will be constructed to direct runoff and drainage from the waste rock material to the interior of the TSF. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 11 4.2.2 TSF Interior Base and Side Slope Design The saprolite at the base of the TSF interior will be excavated to an average depth of about 10 ft (except as noted above in the southeast corner of the TSF), shaped to roughly mirror existing topography, and provide a relatively smooth surface sloped to a single seepage collection sump at the southeastern corner of the TSF. Following base grading and compaction, a TSF base drain system will be installed over the prepared TSF base to collect and remove runoff from the TSF base, runoff and seepage from the waste rock perimeter berm, infiltrating meteoric water, and any collected seepage from upwelling groundwater. Groundwater modeling (SRK, 2024) and water balance modeling (SRK, 2024) have determined that a pumping capacity of 200 gallons per minute (gpm) is adequate to evacuate the TSF sump on a daily basis when subjected to the 100-year storm event. To facilitate pumping from the seepage collection sump at the base of the TSF,an 18-inch pipe will be installed along a ramp on the internal embankment side slope down to the seepage collection sump. 4.3 Phase 3: Operations 4.3.1 Raise Construction Raise construction will be an annual exercise throughout the life of the facility.The starter embankment constructed prior to process startup is expected to provide tailings storage capacity for the first year of operation. During that first year of processing, the first annual raise will be constructed, and so on through the sixth year of operation, which will provide sufficient tailings storage capacity through the eighth year of operations. Beginning with the first year of construction after the starter embankment, each annual raise will be a downstream lift constructed from the toe up to and over the crest with run-of-mine waste rock. The crest width will be maintained at 40 ft(including safety berms and travel ways)for each raise. The currently proposed annual construction targets are aimed at providing a minimum freeboard within the TSF embankment above the highest tailings level of 4 ft. Based on the operational methods described below, actual storm storage capacity will be much greater, as the tailings surface will be sloped to manage stormwater at a surface collection sump. During raise construction, grading will maintain containment of runoff and seepage from the waste rock face inwards towards the TSF interior. Once final perimeter grades have been achieved, the exterior slopes of the perimeter berm will be revegetated with a minimum of 2 ft of growth media placed in loose lifts and revegetated with an approved seed mix. Best management practices will be implemented to prevent erosion until vegetation is successfully established. Runoff from the exterior slopes will be collected in the previously constructed perimeter channels as non-contact water, routed to the sediment pond for sediment control prior to release to Archdale Creek. 4.3.2 Tailings Placement and Tailings Surface Management Tailings will be delivered to the site in over-the-highway haul trucks and either placed directly at the working face or deposited in temporary stockpiles for management with TSF haul equipment. Tailings will be spread with dozers into 12-inch-thick lifts and compacted. The end goal of the daily placement and grading work is to create a smooth, compacted surface that will promote stormwater flow to a MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 12 temporary stormwater collection point while minimizing the potential for stormwater to collect and pool anywhere else on the tailings surface. Collected stormwater will be pumped from the collection point at the tailings surface directly to the CWP east of the TSF. Water balance modeling of the TSF (SRK, 2024) estimated that a nominal pump size of 1,200 gpm is capable of evacuating the PMF event from the surface of the TSF within about 2 weeks. Under the 100-year, 24-hour storm event, the 1,200-gpm pumping system will remove the ponded water from the tailings surface in <2 days. 4.3.3 Stormwater Management During operations, all stormwater management will utilize the stormwater management infrastructure developed during Phase 2 (Construction). Operation stormwater management at the proposed Archdale TSF will consist of conveyance of NPI stormwater from revegetated or resurface areas around the site to the 30-or 36-inch culvert discharging under 1-85. Perimeter non-contact water will be collected from the perimeter corridor and reclaimed perimeter berm slopes and managed with the perimeter sediment pond before being discharged to the 60-inch culvert discharging under 1-85. All contact water produced from contact with the tailings or waste rock materials will be temporarily collected in the TSF sumps before being pumped to the CWP for monitoring and release to the 30-inch culvert discharging under 1-85. 4.4 Phase 4: Closure SRK's Preliminary Closure Plan (SRK, 2024b) describes tailings facility closure in more detail, which is currently anticipated to include the formation of a mounded top surface of compacted tailings graded to drain to the TSF perimeter at a minimum surface grade of 3%. A minimum of 2 ft of growth media will then be placed in loose lifts and revegetated with an approved seed mix. Best management practices will be implemented to prevent erosion until vegetation is successfully established. Stormwater berms and channels will be installed as necessary to control stormwater flows off of the closed surface and safely route them into the perimeter stormwater management system; riprap lining or channel erosion protection products will be utilized where necessary to manage the final grading configuration. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 13 5 Planned Erosion and Sedimentation Control Practices Sediment and control practices will be implemented at the site for individual components of the Project. Some features, such as non-contact discharge structures, are permanent and will remain after the Project enters the post-closure phase. Other features will be in use during the operational period of the mine (approximately 10 years when the development stage is included). Permanent and operational features of the ECP will be implemented as they are constructed in either the development, mining, or closure phases of the Project and are described in detail below. Additional temporary practices are recommended for the individual components as necessary during their initial construction and will be detailed in the individual ECPs that will be developed as the Project advances to the design stage. Activities associated with the Archdale TSF include: • Removal and stockpiling of growth media from the area in the footprint of the TSF • Installation of silt fences, prior to construction,downgradient of the TSF perimeter access road, the NPI area, and the light vehicle access • Management of runoff from active construction areas • Construction of the haul road roadside channel • Construction of the raised berm around the TSF • Stabilization and revegetation of the slopes and grading Specific practice numbers identified in the erosion and sediment control practices reference the NCSCC(2013), Chapter 6, Practice Standards and Specifications.The attached Drawing C-1 presents the location of these facilities and the planned erosion control measure proposed for the Archdale TSF. 5.1 Permanent Development- and Operational-Stage Practices During the pre-development, development, and mining stages of the Project, surface water management structures will be developed to control flows and sediment during the life of the Project (operational) or during operations and through the post-closure (permanent). Operational controls will be removed or reconfigured during the closure stage of the Project. 5.1.1 Permanent Sediment Control Pond Permanent sediment basins are designed to serve areas larger than 5 ac and remain in function for longer than 1 year. One permanent pond will receive non-contact water flows from disturbed and undisturbed natural ground collected by the perimeter channels and release the waters into the existing Archdale Creek. Table 5.1 presents a summary of the sediment pond with its main characteristics. According to the NCSCC (2013), the following design criteria applies to sediment basins (ponds): • The minimum basin volume will be determined based on 1,800-cubic-foot (ft3) of storage per acre of disturbed land. • The minimum surface area will be determined based on 425 square feet (ft2) per cubic foot per second (cfs) of the 10-year peak flow. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 14 As per the North Carolina Mining Manual, "in the Coastal Plain and Piedmont regions, the above equation has been shown to provide a trapping efficiency of 75% or greater for the 40-micron particle: • At a minimum, design the combined spillway system for the sediment basin to be capable of passing the 25-year storm event for the total drainage area. • The minimum dewatering time for the pond is 48-hrs and will require 3 baffles unless less than 20 ft long." Table 5.1: TSF Sediment Pond Volume and Surface Areas Parameter Value Required Contributing watershed 64 ac Maximum 100 ac Top width 500 ft Top length 90 ft Crest elevation 877 ft Length-to-width ratio 5.6 Minimum 2:1; maximum 6:1 Pond slopes 2H:1V Bottom elevation 865 ft Spillway invert 870.5 ft Depth to spillway 5.5 ft Minimum 2 ft Area at spillway 0.696 ac 0.695 ac Volume at spillway 3.11 ac-ft 2.64 ac-ft Spillway width 50 ft Skimmer size 8-inch float/6-inch orifice Nominal skimmer flow 0.854 cfs/383 gpm Time to dewater 51 hours Minimum 48 hours Source:SRK,2023a The Archdale perimeter sediment pond will receive runoff from up to 65 ac of disturbed land, which includes perimeter roads and berms, haul roads, and other mine disturbed areas. Figure 3.1 shows the location of the pond, which will be configured as a skimmer pond. 5.1.2 Sediment Fence (Practice 6.62) Sediment fences will be placed around disturbed surface during construction activities (as indicated on Figure 3.1) to minimize sediment from entering the non-contact channels. Sediment fences are anticipated during: • Clearing and construction of the TSF • Construction of haul roads, non-contact diversion channels, sediment ponds, and other mine infrastructure • Construction of the process area and non-process area sites 5.1.3 Permanent Grass-Lined Channels (Practice 6.21 and Practice 6.30) Permanent non-contact diversions channels will be constructed to route non-contact flow through the Project area, as described in Section 9.Where calculations indicate that grass-lined channels will have adequate erosion resistance, these channels will be stabilized and revegetated as part of the channel construction. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 15 5.1.4 Permanent Riprap-Lined Channels (Practice 6.21 and Practice 6.31) Permanent non-contact diversions channels will be constructed to route non-contact flow through the Project area, as described in Section 9. Where calculations indicate that riprap-lined channels will be required to provide adequate erosion resistance, these channels will be constructed with riprap channel armoring. 5.1.5 Permanent Outlet Protection Level Spreader (Practice 6.40) The sediment pond will discharge into Archdale Creek using a skimmer as well as an emergency spillway. The outlet pipe from the skimmer and the discharge from the emergency spillway will both utilize level spreaders at the discharge point into Archdale Creek to minimize erosion. 5.1.6 Operational Dust Control (Practice 6.84) Haul traffic on dirt roads between the mine facilities will be ongoing during the mine development, operations, and closure activities and will require regular application of water for dust control. Dust control water will be supplied by dewatering of the existing pit lakes during construction and placement. Air monitoring will be implemented at the site to evaluate the effectiveness of the dust control and adjust sprinkling application rates as necessary to meet Mine Safety and Health Administration (MSHA) guidelines. 5.1.7 Operational Temporary Seeding (Practice 6.10) Operational stockpiling of growth media will occur throughout the life of the Project as mine facilities are developed or incrementally expanded. Where suitable growth media can be harvested from the surfaces during the facility development, the growth media will be stockpiled in designated areas. The stockpiled growth media will be used during concurrent closure and final closure activities, as described below. As the stockpiles achieve their ultimate shape, the surfaces will be temporarily vegetated to minimize erosion. 5.2 Closure Stage Practices When mine facilities have achieved final surface configuration, it may be feasible to apply progressive closure activities to limited areas of the Project while mining operations are still active elsewhere at the site. Progressive closure plans will be developed as the mine design progresses. Regardless, at the cessation of mining, closure activities will remove operational infrastructure and upgrade or add additional features to the mine facilities to provide for long-term stability. A preliminary closure plan for the facility Project has been developed (SRK, 2024b) and will be refined and updated as the Project design is advanced. General measures that will be included in the mine plan are described in the following subsections. 5.3 Temporary Development Stage Practices During all stages of the Project, mine facilities will be developed, which will include clearing and grubbing, growth media removal and stockpile, grading, and establishing permanent or semi- permanent surfaces. As the final designs for these activities are developed, individual ECPs will be developed that implement temporary sediment control measures necessary until the permanent or operational controls are in place. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 16 5.3.1 Temporary Dust Control (Practice 6.84) Dust control during the construction of the mine facilities will be addressed through the regular sprinkling of water on the surfaces. A fleet of water trucks equipped with sprinkler attachments is included in the mine operational fleet and will be utilized to limit dust during earthworks activities. 5.3.2 Temporary Sediment Traps (Practice 6.60) Temporary sediment traps consisting of rockfill berms will be placed in the diversion channels to control sediment releases until vegetation can be established in the disturbed area. 5.3.3 Sediment Fence (Practice 6.62) Sediment fences will be placed around disturbed surface during construction activities prior to revegetation to minimize sediment from entering the non-contact channels. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 17 6 Maintenance Plan Regular maintenance practices are important to prevent adverse negative impacts to the environment. Routine inspections of all sediment control facilities will be conducted at least once per week and after every rainfall event that results in observable runoff. An inspection report template will be prepared. Based on the observations, the following activities will be conducted. • Sediment pond: o All erosion and sediment control measures, including the sediment pond, seepage ponds, check dams, and silt curtains, will be checked for stability and operation. Any needed repairs or adjustments will be implemented immediately. o The sediment pond will be cleaned out when the sediment accumulation reaches 50% of the available storage. The cleanout level will be pre-determined in the inspection report. o Floating trash and debris will be removed. o Vegetation at the top and faces of the embankment will be removed. o All outlet structures from the sediment pond will be inspected for clogging and/or structural damage. Debris will be removed, and any repairs needed will be done immediately. Outflow locations will be inspected to make sure tailwater conditions are not impeding discharge from the pond. • Check dams: o Remove sediment adjacent to and accumulated behind check dams before it reaches halfway to the top of the dam. o Restore dislodged or washed-out check dams to their original configuration. o Fill in or otherwise repair areas where check dam undercutting or bypasses have occurred. o Add stones to dams as needed to maintain design height and cross-section. Use larger stone, if necessary, to counter higher-than-expected flow velocities. o Repair ditch/channel areas where excessive downcutting or side scour have occurred. o Make notes on whether the selected configuration is preventing channel erosion. If not, make the necessary changes to the design, considering other materials or closer spacing in areas experiencing the most problems. o If significant erosion is observed between dams, install a protective turf reinforcement mat or section of riprap liner in that portion of the channel. o Replace rock weirs when filtering capacity is reduced by one-half. • Riprap channels: o Riprap channels will be inspected at least once per year and after every major storm event for displaced stones, slumping, and erosion at edges, particularly in steeper segments. o Woody vegetation will be annually removed from the riprap to avoid potential impacts associated with the roots, such as dislodgement of rocks. • General guidance: o Field markers will be placed to denote areas of concern and in need of repairs or maintenance. o A plan to access appropriate riprap (e.g., on-site stockpiles) will be in place to allow for timely repairs of eroding channels. o For each inspection, the inspector should bring a copy of the as-built drawings to mark potential corrections and problem areas. The marked-up drawings will be stored digitally MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 18 to confirm that the works needed were completed in subsequent inspections. The reports will also include photographic records to document the following: - Vehicle access - Overview of facility - Overview of spillway - Overview of discharge infrastructure - Upstream view of the facility - Downstream view of the facility MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 19 7 Detail Drawings and Specifications for Practices Specified References have been made to specific sections of the NCSCC. Detail drawings and specifications will be provided in the next stage of design. This section includes preliminary sketches to illustrate the recommended practices. Figure 7.1 shows a typical drawing of a permanent skimmer basin, representative of the sediment pond. Calculations to support the design of the Sediment Pond are presented in Appendix B of the main report(Table 6). 5MMMER SEDIMENT BASIN PLAN VIEW BAFFLE �I�llj�I�llj 3RD BAFFLE: DESIGN CRITERIA I1=— =— —I — SURROUNDING MIN. SKIMMER LENGTH TO 2:1 — WIDTH RATIO NOTES: Max LENGTH TO fi:1 WIDTH RATIO 1 REFER ADDfTIONOAL MS4 FOR DESIGN SEDIMENT U F VOLUM�RAGE CU FF. INFLOW SPECIFICATI___ BARREL RECARDNG SNS EDIMENT VOLUME PER AC. STRUCTURE REQUIRED DISTURBED 10� - -- PIPE BASINS_ 180D MIN. DEWATERING CU.FF =_ -_ 2. FORERAY, IF REQUIRED _____ VOLUME (67 CU.7C.) BY M54, IF NOT ADD REQUIRED PER AC. ISER THIRD BAFFLE. TOTAL SURFACE 325 SKIMMER AREA SQ.FT.PER ATEDEVICERING ICI REQUIRED CFE 010 MINIMUM — DEWA7ERINC 48 HRS TIME _ F EQUAL MAXIMLM WIDTH ALLUWEB MUST DEWATERING 120 HRS _ CONFIRM MEETS TIME — — — — FLOW RATE RANGE CROSS—SECTION VIEW SEE NDTE 02 —IIII�III— - — SPECIFIED, OEWATER140 ZONE PRIMARY SPILLWAY(RISER) 5' MIN NORMAL WATER EMBANKMENT INFLOW ELEV. STRUCTURE 1.0, MIN. BAFFLE 'MIN. OUTLET INVERT — — FREEBOARD SEDIMENT DEW TIERING BASIN STORAGE VOL. VOLUME NU. REQ. PRPV, REQ. PROV, III—III—III— — — — EMERGENCY (OF) (CF) (CF) (CF} T��I�ILTIII_ _ _ I—III— — i 1 1 I, — III — I I— r' FILTER FABRIC ANTI-SEEP SEDIMENT NOT TO SCALE DATA BLACK STORAGE ZONE BOTTOM BASIN ELEv. BASIN EASIN DRAINAGE JISTJR3EJ Qe SURFACE AREA BOTTOM OUTLET BARREL Top OF EVE,. EMER. SKIMMER SKIMMER SKIVMES EUUAL SKIMMER NO AREA AREA (CFS) REQ- PROV OF BASIN INVERT PIPE USER SPILLWAY SPILLWAY SIZE ORIFICE TYPE ALLOWED" FLOW RATE (ACRES) (ACRES) (" (CF} (ELEV,) (ELE V.) (SIZE) (ELEV) [ELEV.) [WIDTH) DIAMETER YES NO MIN. MAX. MARLEE MARLEE RYMAR WWW.��5)—ERWRD33S.COM SKIMMER & RISER SEDIMENT BASIN WITH PERMANENT WET POND REV 12 04 22 Source: Rymar Float,2024 Figure 7.1: Skimmer and Riser Sediment Basin with Permanent Wet Pond Figure 7.2 shows check dams, and Figure 7.3 shows permanent and operational riprap-lined channels (Practice 6.21 and Practice 6.31). MH/DH April 2024 SRnConevmng(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 20 L = The distance such that points A and B are of equal elevation 15 min. 9"min At Filter Cloth Plan View washed stone 15 center Fi[ter Cloth Cross-5ection View Source: wCSCC.co1n Figuna7.2: Rock Check Dam mmov Apm2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 21 Trapezoidal Riprap Channel Design top width Design depth y:4 11 Oil- Filter layer, gravel or fabric Source: NCSCC,2013 Figure 7.3: Typical Riprap Channel Cross-Section Figure 7.4 shows permanent and operational outlet stabilization structure (Practice 6.41), and Figure 7.5 shows operational paved flume (Practice 6.33). MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 22 Pipe Outiat to Flat Area— No Well defined Channel 3d0 A A do Plan If La ,�L Ik=II �ITI�Ad u lali�l` r. I Section AA *Filter Notes blanket i. La is the length of the riprap Pipe Outlet to Well-defined apron. Channel 2- d= 1.5 times the maximum stone diameter but not less than 6"_ 3. In a well-defined channel ex- tend the apron up the channel banks to an elevation of 6" A A ---- above the maxim urn tailwater depth or to the top of the bank, whichever is less. 4. A filter blanket or filter fabric should be installed between Plan the riprap and soil foundation. ;¢ La �a I Ad_EI ` N-IR , �4111i1 'II Section AA �I I uti 41i1� Filter blanket Figure 6.41c Riprap outlet protection(modified from Va SWCC). Source: NCSCC,2013 Figure 7A Outlet Stabilization Structure MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 23 Emergency ,,1`4,`A; bypass flowIN !��, �'�:• 1., - ,,� n.��'xt1�`1A `�,1, r'�• •\tom�`` \`.��:SIB` -• . Is vV r. r Expansion joint Source: NCSCC,2013 Figure 7.5: Typical Operational Paved Flume MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 24 8 Vegetation Plan In accordance with the North Carolina Application for a Mining Permit, a reclamation plan must include plans for year-round seeding, including the time of seeding and the amount of seed, type of seed, fertilizer, lime, and mulch per acre. The recommendations must include general seeding instructions for both permanent and temporary revegetation. Table 8.1 includes a preliminary seed mix and schedule provided by SWCA Environmental Consultants (SWCA) (2023). Table 8.1: Preliminary Seed Mix Composition and Schedule Seed Mix Type Seeding Dates Seeding Rates NC Steep Slope Mix ERNMX-310 All dates 45 pounds Ib/ac Native Habitat Strip Mine Mix ERNMX-111 All dates 20 Ib/ac Native Steep Slope w annual rye ERNMX-181 February 15 to August 15 60 Ib/ac Native Steep Slope w grain rye ERNMX-181-2 August 15 to February 16 75 Ib/ac Source:SWCA,2023 Temporary cover species for erosion control will include: • Brown Top Millet: February 15 to August 15, 20 Ib/ac • Annual Rye Grain: August 15 to February 15, 30 Ib/ac No fertilizer is recommended at the site due to the success of volunteer regrowth seen during site visits.Seed will be procured from Ernst Conservation Seeding or another approved seeding contractor. Wildlife habitat is typically established by creating ecosystems of native species and reshaping landscapes to create suitable habitat. Monitoring and measurement criteria for vegetation and wildlife success will be developed as mine plans progress. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 25 9 Supporting Calculations Hydrological and hydraulic calculations were primarily conducted using a HEC HMS model developed for the Project and are included as appendices to the storm water management plant. Appendix B of that document presents a summary of hydrological and hydraulic calculations and modeling results used for the design of erosion and sediment control measures. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 26 10 Financial Responsibility/Ownership Form MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 27 11 Checklist MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 28 12 References Environmental Systems Research Institute, Inc. (ESRI), 2023. Garrett, 2004. Global Industry Standard on Tailings Management (GISTM), 2020. Horton and Butler, 1988. North Carolina Erosion and Sediment Control Planning and Design Manual (NCSCC), 2013. North Carolina Sedimentation Control Commission, North Carolina Department of Environmental and Natural Resources, and the North Carolina Agricultural Extension Service. Erosion and Sediment Control Planning and Design Manual, May 2013. North Carolina Surface Mining Manual, 1996. State of North Carolina, Department of Environment, Health and Natural Resources, February 1996. SRK Consulting (U.S.), Inc. (SRK), 2023. SRK, 2023a. SRK, 2024. SRK, 2024a. Design of the Archdale Tailings Facility, March 2024. SRK, 2024b. Conceptual Report Closure Plan Kings Mountain Mining Project September 2023 Rymar Float, 2024. Webpage: https://rvmarwaterworks.com/marlee-float. SWCA Environmental Consultants (SWCA), 2023. Biological Resources Summary Report for the Kings Mountain Lithium Mine, Cleveland County, North Carolina Interim Draft, prepared for Albemarle U.S., by SWCA Environmental Consultants, Colorado, April 2023. MH/DH April 2024 SRK Consulting(U.S.), Inc. Erosion and Sediment Control Plan Template—Kings Mountain Page 29 Disclaimer The opinions expressed in this Report have been based on the information supplied to SRK Consulting (U.S.), Inc. (SRK) by Albemarle Corporation (Albemarle). These opinions are provided in response to a specific request from Albemarle to do so, and are subject to the contractual terms between SRK and Albemarle. SRK has exercised all due care in reviewing the supplied information. Whilst SRK has compared key supplied data with expected values, the accuracy of the results and conclusions from the review are entirely reliant on the accuracy and completeness of the supplied data. SRK does not accept responsibility for any errors or omissions in the supplied information and does not accept any consequential liability arising from commercial decisions or actions resulting from them. Opinions presented in this report apply to the site conditions and features as they existed at the time of SRK's investigations, and those reasonably foreseeable. These opinions do not necessarily apply to conditions and features that may arise after the date of this Report. Copyright This report is protected by copyright vested in SRK Consulting (U.S.), Inc. It may not be reproduced or transmitted in any form or by any means whatsoever to any person without the written permission of the copyright holder, SRK. MH/DH April 2024