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Home My WebLink About20190035 Ver 1_More Info Received_20190905F]J PIEDMONT LIT H I LIM September 5, 2019 Ms. Olivia Munzer NC Wildlife Resources Commission Rogers Depot, 1718 NC Hwy 56 West Creedmoor, NC 27522 Subject: Piedmont Lithium Project (SAW -2018-01129) Additional 10 Day Agency Comment Period On behalf of Piedmont Lithium, Inc., HDR would like to thank you for your questions that arose during the additional 10 day comment period that began on August 20, 2019, and ended on August 30, 2019. The NC Wildlife Resources Commission provided the eight questions below in an email format. 1. Will they mine any of the pits simultaneously during the life of the mine? Yes, it is anticipated that as many as two pits will be open at any given time. According to the current mine plan the mine sequence will be east pit, south pit, central pit, then north pit. Additionally, once its reserves are exhausted, the east pit will be backfilled with waste rock. 2. Table 2 refers to PW -1 groundwater baseline. I was unable to find its location on a figure. PW -1 is the aquifer pump well and is located north of Hephzibah Church Road and north of the East Pit. LEGENDi'-# IP Project Boundary 0 (963 ac.) Pit Extents Pumping Well A Observation Well Gaston Co. Receptor ~ Well HDR Delineated Streams 0 HDR Delineated Pond HDR Delineated 0 Wetlands Desktop Streams ® Desktop NWI Wetland 100 -Year FEMA (�\ Floodplain T� Culverts t —h -1 600 f—t - N t -Mw-1 MW -5 �9 WON. 0 Feet 1.800 _ 'ir' f MW -4 - O s • i Figure 1. Location of Pumping Well, Observation Wells, and Receptor Wells. OW -21) W-25 PW -1 \ OW -1D OW -15 41 F]J PIEDMONT LITHIUM 3. It appears that the stream flow was only measured in May. Can they explain as to why it wasn't measured during other times of the year (high and low flow)? We noted that there was only one measurement and that it was not during low flow. All available data was provided to support the model, which presents the greatest amount of drawdown or withdrawal at the full excavation limit of each mine pit, in effect, the worst-case scenario as noted in Question 5, below. Given timing, project schedule, and project budget it was measured at the time noted. 4. What is the distance from the outflow (energy dissipater) to the streams? Please see the attached table with the requested information. Figure 1 in Appendix C in the Public Notice Response (dated May 31, 2019, revised July 3, 2019) is also attached, depicting the proposed outflow locations. 5. How long will the pits be in operation? The dewatering model assumes a steady state withdrawal, therefore a reduction in baseflow, for the entire timeframe that each pit is being mined. I'm assuming that will be years, but is it 5 years, 10 years, more? The anticipated total life of mine under the proposed plan is 11 years; but that may be adjusted, including increased, based on the actual declaration of reserves. We also note that the hydrogeological model presents the greatest amount of drawdown or withdrawal at the full excavation limit of each mine pit. This is in effect the worst-case scenario with respect to drawdown. Dewatering therefore should be less than the figure presented until the pit excavation approaches its ultimate pit shell. Additionally, once each pit is exhausted and mining operations or waste backfill operations have concluded, dewatering will cease in that pit. Pits will be allowed to flood at the conclusion of operations. 6. They say the dewatered pit water will be applied to streams or wetlands within the project boundary. So, I would assume the net outflow from the site may actually be higher than normal while the pits are active. Can they confirm this? It is possible that the net total outflow from the site will be greater than normal in the presence of dewatering operations. 7. I'm not clear on how they are defining baseflow, which is what they are using as the denominator for comparisons. Are they assuming baseflow is a static number or if it changes seasonally? My understanding is the latter. If I'm correct, then the percentage impact will vary through the year. So, does their characterization of (up to) a 10% reduction in baseflow represent a full and complete understanding of the impacts? Base flow is the groundwater that discharges to the stream and should not vary seasonally throughout the year, but base flow could be affected by long term climate events, such as droughts. Variability in stream flow is usually from runoff and evapotranspiration, while base flow remains constant. Since base flow only is the lowest flow condition, the model estimates the greatest amount of impact (estimated worst case scenario) that should be seen. Here is an explanation of base flow from the USGS: https://www.usgs.gov/special- topic/water-science-school/science/base-flow-rivers?gt-science center objects=0#gt- science center objects P I E DMON T LITHIYM 8. There are limited data points. They state they are willing to do additional data collection and model refinement. Is that something they can do and in what timeframe? Having worked extensively on the model presented, we respectfully believe that the data presented is adequate and a good representation of potential effects the proposed activities may have on groundwater. In fact, the model assumes the worst-case scenario with respect to drawdown and it does not take into account the continuous input of water from offsite. It is likely that potential effects may be less than modeled. Additional data collection, specifically pump tests, and modeling are not likely to result in a model with greater accuracy, or present results which are likely to show greater impacts than those currently presented. Piedmont has collected groundwater and surface water quality data for a number of months, which was submitted (data up to that point) with the Public Notice response on July 3, 2019 (dated May 31, 2019, revised July 3, 2019). This data collection has continued and will continue through the end of the year. On behalf of Piedmont Lithium, Inc., HDR is submitting this response to the eight questions that arose during the additional 10 day, agency comment period. Should you have any questions or require additional information following your review of the enclosed materials, please contact me at (704) 338-6710 or kelly.thames(@hdrinc.com. Sincerely, HDR, Inc. Pell�_,�ames, PWS Environmental Project Manager Attachments: Tabulated Outflow Distances to Streams Piedmont Lithium Site Plan Map cc: Patrick Brindle, Piedmont Lithium, Inc. ARSHUL ILLE [sem 11 ENERGY DISSIPATOR TO STREAM - FLOW DISTANCE PROJECT PIEDMONT LITHIUM BY CFH DATE 9/5/19 SHEET 1OF1 PROJECT NO. PLIT101 CHECKED BY JAA DATE CHECKED 9/5/19 Pond Flow Distance to Jurisdictional Stream (ft.) EWR SEDIMENT POND 1 414.92 EWR SEDIMENT POND 2 56.95 EWR SEDIMENT POND 3 1209.55 WWR SEDIMENT POND 1 229.72 WWR SEDIMENT POND 2 778.48 WWR SEDIMENT POND 3 37.78 WWR SEDIMENT POND 4 149.32 WWR SEDIMENT POND 5 44.86 SEDIMENT POND SB1 18.54 SEDIMENT POND SB2 38.83 SEDIMENT POND SB3 10.95 SEDIMENT POND SB5 95.14 PIT DISCHARGE POND N 92.44 PIT DISCHARGE POND CN 226.84 PIT DISCHARGE POND CS 184.99 PIT DISCHARGE POND S 427.79 PIT DISCHARGE POND E 324.82 MAINTENANCE AREA FUEL YARD BAH HZICHURCH RD �� -;PTO THRU TRAFFIC �OIICAL USE ONLY O HEPHZIBAH CH RCH RDI- ,., CLOSED ;� aE c No. 2 Gp@"CPNWEBBEC"u" G NOTES: 1. Sequence of pit clearing to include stripping of East Pit, South Pit, Central Pit, and North Pit. Sediment/Erosion G ontrol for pit clearing stages to involve placement of SU silt fence (steel piles) in downslope areas of pits. 2. Disturbed ground during bridge Construction, through the use of Best Management Practices (BMP) (e.g. sediment fences, erosion control structures diversion ditches, silt fence and revegetation measures), runoffwill be J intercepted before it �- is able to reach the creek. Sediment yield from disturbs areas will be managed by sediment Control structures and temporary and permanent vegetal on, such that any added sediment load to the Creceiving stream is expected to be minimal during construction activities. Drainage control structures, along with the Contemporaneous regrading and revegetation of disturbed areas are expected to prevent or minimize the �contributions of suspended solids. All disturbed areas will �-'-� be seeded as quickly as possible. Once the bridge construction is completed, disturbed areas will be reclaimed to further minimize runoff. E- SCREENING NcBE�oNO S��,��/!/ wwR SE POND Nab WEST WASTE ROCK DISPOSAL AREA OB -5 ..MTSOFExcnvn.ON / EITCET b O ON.SS ENTPO 6 �. ✓ ry rip, C, Ex sTNG TRFAM CRONG C uMENo. n o Tr ° pISCHAR /r� I :� a, s � e Ta PLANT TG RTRFT �es� .�pNGRETER wnccleoTN EH 7�'/ EAST WASTE RO DISPOSAL AREF.j .a .o TRrrT OB -0 pp ROA o b* 3 Porno A L UTI PIT G / wwRaEG�N NG� I i i sTa �.1 FENCE/ _ 6 FEET HIGH vnvR N C e TCH - ratio nccwt.s�II' N --- '� _ �) / \ ........ 2 WNR ' k CH N 1 :tGH FLUME m�wwR DT 611 �S�� R r coNOAcc sRGAG NE 40,6 z E MTSG�s aEXCAVATIO LGwwATER asING - I i -arm uT 3 a NNo IC CETTRALrTTGR .� EwRaEDM sE IHITESIDE RD...... APROPOSE _x g ,.- ... ENCE m O �t CLOSED 1 �'O T `' 6 FEET HIGH i t six, I — gaNRT ° II ,`UNITS°FE �A�ATG a'AN� --II 6 FEET HIGH i ru t H111 Ik _\ PROPOSED SEE NOT '✓ �� ,y 23 OB -3 i MINE PT CONSTRUCTION SEQUENCE SEE NOTES .!� � Q LEGEND \/ 11 /, ti y" 100 YR. FLOOD PLAIN � DELINEATED WETLANDS DELINEATED PONDS DELINEATED STREAMS ' ` _ -==I- PROPOSED DITCHES _- PROPOSEDFLUMES .. .. .o BUILDING/STRUCTURE EWR DISPOSAL AREA WWR DISPOSAL AREA _ - EXTENTS OF MINE PITS AND EXCAVATION ASTINGS RD. HAULROAD CULVERTS .., �,. CLOSED HAULROAD SUMPS RECEPTOR WELLS ; ROADCLOSURE a� SUPER SILT FENCE O � OBSERVATION WELL DO PIEDMONT PROPERTY LINE \ / MINE PERMIT LINE 25 FT MINE PERMIT BUFFER FT LOT BUFFER 200 FT STRUCTURES BUFFER RESIDENTIAL BUFFER SITE / MINE MAP PLAN VIEW ,... _ HEPHZIBAH C URCH RD. CONTOUR rNrEBVAL=zFEET CLOSED ,...._._ o M 60 No —41 1- SCALE 1"•100' Dv[e Revision DESIGNED: JDP, COS PIEDMONT LITHIUM, INC. DRAWN : dDP, cos SHEET PIEDMONT LITHIUM CHEKEDi 24/ P I E DIy1Q N T LINCOLNTON WEST QUADRANGLE DATE: AS SHOWN 19 OF 1 SCALE - AS HOWN GASTON COUNTY, NORTH CAROLINA PROJECT NO.: PLIT101 LITHIUM FILE ND.. —11 -Bluefield, VA May, 2019 JP SM CS JA