Appendix D. Hydrology and Hydraulics

Transcription

1 Appendix D Hydrology and Hydraulics

2 TECHNICAL MEMORANDUM Date: February 13, 2014 Document No.: To: Paul Bergstrom Company: Rare Element Resources From: Micah Richey cc: Tammy Rauen and Roman Popielak RE: BEAR LODGE PROJECT, BULL HILL MINE PRE-FEASIBILITY HYDROLOGY AND HYDRAULICS, REVISION E 1.0 INTRODUCTION Rare Element Resources (RER) is proposing a new open-pit mine for rare earth materials north of Sundance, Wyoming referred to as the Bear Lodge Project, Bull Hill Mine. This memorandum describes pre-feasibility level hydrology and hydraulics calculations for the site. The calculations were performed in order to develop the framework for an initial stormwater management plan for the site, encompassing possible stormwater diversions, runoff collection channels, haul road culverts, and sedimentation ponds. 2.0 METHODOLOGY 2.1 Hydrology Calculations Peak stormwater flow rates contributing to, or otherwise impacting the proposed facilities at the Bear Lodge Project were estimated for the 100-year frequency, 6-hour duration storm event in accordance with the Wyoming Department of Environmental Quality, Land Quality Division s Guidelines (WDEQ). Using the site topography provided by RER, basins were delineated for the Mineable Pit, Waste Rock Facility (WRF), Haul Roads, and Plant Site (see Figure 1). The time of concentration for each basin was then estimated using TR-55 methodology (NRCS, 1986). Curve numbers for the site were assigned using TR- 55 methodology (NRCS, 1986) in conjunction with soil survey information (NRCS, 2011). The 100-year frequency, 6-hour duration, and 10-year frequency, 24-hour duration storm depths were estimated for the site from the NOAA Atlas 2 (NOAA, 1973). Hydrologic modeling was then performed using the Hydrologic Engineering Center s Hydrologic Modeling System (HEC-HMS) (USACE 2010) to calculate runoff volumes and peak flow rates. 2.2 Preliminary Sediment Pond Sizing In accordance with the Wyoming Department of Environmental Quality Water Quality Rules and Regulations, Chapter 11, Section 31, the sediment ponds are sized to accommodate runoff from the 10- year frequency, 24-hour duration event, which was modeled using HEC-HMS (Wyoming DEQ 2012). Additionally, the ponds are sized to accommodate the expected sediment. In accordance with Michigan Department of Environmental Quality guidelines, the sediment pond are sized, at a minimum, to contain I:\11\82323\0100\0122 TM\Feb14\ TM PreFeasibilityHydrologyHydraulicsRevE 13FEB14.docx Golder Associates Inc. 44 Union Boulevard, Suite 300 Lakewood, CO USA Tel: (303) Fax: (303) Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation

3 Paul Bergstrom February 13, 2014 Rare Element Resources the volume of sediment equal to one inch of runoff from the entire catchment area, or 3,630 ft3/acre of sediment (Michigan DEQ 2012). In addition to storage for environmental flows from the pit and Basin Pt-N, the Pit Pond is also sized to accommodate pit dewatering flows of 500 gallons per minute (gpm). The pond water and sediment capacity is estimated using an assumed retention time (2 days) and settling velocity parameters based on particle size. 2.3 Channel and Culvert Hydraulics Channel sizing calculations were performed with an open channel flow spreadsheet using Manning s equation. Riprap sizing was performed using U.S. Army Corps of Engineers methodology (USACE, 1994). Culvert crossings were modeled using HY8 culvert analysis software (FHWA 2011). 3.0 ASSUMPTIONS Runoff from the top of the WRF travels down the 1-percent slope to the north and south then cascades perpendicular to the slopes, and is collected in a perimeter channel at the toe of the facility Haul Road culvert crossings were located based on the proposed road alignments and topography supplied by RER All calculations assume the following facility conditions: Full build out of the Pit and WRF The WRF is in a closed condition with 50-percent of the area reclaimed The Low Grade Ore (LGO) stockpile has been processed and either been sent to the Upton facility or added to the footprint of the WRF All runoff from the plant site is collected for discharge to a sedimentation pond Time of concentration for both the Plant Site and the Mineable Pit are assumed to be 10 minutes Channel lining criteria: Design Flow Velocity (ft/s) Channel Lining Material <5 Grass 5 15 Riprap >15 Concrete, Articulated Concrete Block Curve Numbers Used in hydrology calculations (NRCS,1986, Web Soil Survey): Description of Soil & Land Cover Woods-Grass Combination, HSG B, Fair Cover SCS Curve Number Applicable Site Areas Undisturbed or Reclaimed areas Newly Graded Areas, HSG B Disturbed Areas, Pit, Unreclaimed WRF, and Plant pad I:\11\82323\0100\0122 TM\Feb14\ TM PreFeasibilityHydrologyHydraulicsRevE 13FEB14.docx

4 Paul Bergstrom February 13, 2014 Rare Element Resources Storm Depths (NOAA, 1973): Storm Event 2-year 24-hour 10-year 24-hour 100-year 6-hour Storm Depth (in) Applications Tc Calculations Sedimentation Pond Volumes Conveyance Channel, Riprap, and Culvert Sizing Storm event temporal distribution Dimensionless design mass curve (Tyrell & Hasfurther 1983) Type II storm distribution Manning s n Coefficients: Manning s n Description Stability Capacity Grass Riprap Mountain Stream Corrugated Metal Pipe (CMP) Haul Road Culverts: Culverts are assumed to be corrugated steel with Manning s n = Length, available headwater depth, headwall configuration, downstream channel geometry, and slope are assumed or estimated from available topography Channel Assumptions: Slopes for flow routing and channel sizing calculations are the average slope across the entire reach 3H:1V side slopes Minimum freeboard is 1 ft 4.0 CALCULATIONS Basin area-weighted curve number calculations are presented in Table 1. Time of concentration calculations are presented as Table 2. The HEC-HMS model parameters are included as Attachment A and calculated 100-year frequency, 6-hour duration and 10-year frequency, 24-hour duration peak flows are included as Tables 3 and 3a respectively. Preliminary channel sizing calculations are presented in Table 4. Preliminary riprap sizing calculations are presented in Tables 5 and 5a. HY-8 Culvert sizing model output is included as Attachment B. Pit dewatering pond sizing calculations are included as Attachment C. 5.0 CONCLUSIONS AND DISCUSSION Channel dimensions and revetment have been designed based on available topography and preliminary facility designs. Dimensions and revetment requirements may change as the designs become more detailed. I:\11\82323\0100\0122 TM\Feb14\ TM PreFeasibilityHydrologyHydraulicsRevE 13FEB14.docx

5 Paul Bergstrom February 13, 2014 Rare Element Resources Proposed Stormwater Management Arrangement A berm around the upgradient side of the Mineable Pit highwall (PIT DIV N. and PIT DIV S.) prevents surface water flows from running into the Mineable Reserve pit during the design storm event and diverts the stormwater north and east into the existing drainages. Perimeter channels (as assumed) carry stormwater flows along the north and west side of the WRF to a proposed sediment trapping pond on the north side of the WRF (Pond 1 on Figure 1). Perimeter channel (as assumed) carry stormwater flows along the north and east side of the WRF to a proposed sediment trapping pond on the northeast corner of the WRF (Pond 2 on Figure 1). Perimeter channels (as assumed) carry stormwater flows along the south side of the WRF to a proposed sediment trapping pond on the southeast corner of the WRF (Pond 3 on Figure 1). Parallel diversion channels along the south and west sides of the WRF will divert the undisturbed upper reaches of Beaver Creek along the toe of the WRF and terminate into an upper tributary of Beaver Creek. Perimeter channels along the north and south sides of the Plant Site Pad (labeled PD-N and PD-S, respectively) convey flow to a sediment trapping pond on the east side of the Plant Site Pad. The following table provides a summary of the proposed diversion channels: Reach ID 100-yr/6-hr Peak Flow (cfs) Length Slope (ft/ft) Side Slope (_H:1V) Left Right Bottom Width Depth Freeboard WRF WRF 2a WRF 2b WRF WRF DIV W PIT DIV S PIT DIV N PIT DIV N BC DIV U BC DIV L PD-N PD-S Preliminary Sedimentation Pond Sizing The required volumes for each of the sediment trapping ponds are presented in the table below. The volumes are representative of storage to accommodate runoff from the 10-year 24-hour event and sediment storage. The Pit Pond also includes storage for water and sediment as a result of 500 gpm pit dewatering (calculations presented in Appendix C). The ponds and any associated embankments will be protected by outlet works and overflow spillways to be provided as part of detailed designs. The overflow spillways will likely be designed to flow over the face of the embankment in a controlled manner in a I:\11\82323\0100\0122 TM\Feb14\ TM PreFeasibilityHydrologyHydraulicsRevE 13FEB14.docx

6 Paul Bergstrom February 13, 2014 Rare Element Resources reinforced section. The ponds will require periodic maintenance and cleanout to ensure proper functioning. The required freeboard storage of one foot is not included in these numbers. Sediment Pond Catchment Area (ac) 10-Year Event Volume (ac-ft) 1 Sediment Storage Volume (ac-ft) 2 Total Pond Volume (ac-ft) 3 Waste Rock Facility Pond Pond Pond Pit Pond Environmental Flows Pit Dewatering PUG Plant PUG Plant Pond Notes: 1. In accordance with the Wyoming Department of Environmental Quality Water Quality Rules and Regulations, Chapter 11, Section 31, the sediment ponds are sized to accommodate the 10-year 24-hour runoff event. The design storm event was modeled using the Hydrologic Engineering Center's HEC-HMS program. Additionally, the ponds must be sized to accommodate the expected sediment storage. 2. The annual volume of sediment generated was assumed to be equal to one inch of runoff from the entire catchment area. This corresponds to 3,630 ft³/acre. 3. Total pond volume represents a neatline volume and does not include the required freeboard. 5.3 Haul Road Culvert Sizing Estimated culvert sizes are summarized in the table below. Culvert Designation (See Figure 1) Design Flow (cfs) Culvert Size (in.) Length No. of Barrels D D I:\11\82323\0100\0122 TM\Feb14\ TM PreFeasibilityHydrologyHydraulicsRevE 13FEB14.docx

7 Paul Bergstrom February 13, 2014 Rare Element Resources REFERENCES Association of State Dam Safety Officials (ASDSO) (2000): n. pag. Online. Internet. 20 January Available: HEC-HMS Hydrologic Modeling System [computer software] August 2010 US Army Corps of Engineers Version 3.5 Natural Resource Conservation Service (NRCS) Urban hydrology for small watersheds, 2nd edition (USSCS Technical Release Number 55). Washington D.C.: United States Department of Agriculture. Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at Accessed January 20, Tyrell, Patrick T. and Hasfurther, Victor R. Design Rainfall Distributions for the State of Wyoming. Department of Civil Engineering, College of Engineering, University of Wyoming. August U.S. Army Corps of Engineers (USACE) Hydraulic Design of Flood Control Channels. Engineer Manual Department of the Army. Washington D.C.: United States Government Printing Office. U.S. Federal Highway Administration (FHWA) HY8 Culverts Version FHWA Culvert Analysis. Washington, DC: FHA Office of Technology Applications. U.S. National Oceanic and Atmospheric Administration (NOAA) Precipitation Frequency Atlas of the Western US, Atlas No. 2, volume II Wyoming. Silver Spring MD: US Department of Commerce. Wyoming Department of Environmental Quality, Land Quality Division (WDEQ): Chapter 11, Section 31. Available: I:\11\82323\0100\0122 TM\Feb14\ TM PreFeasibilityHydrologyHydraulicsRevE 13FEB14.docx

8 TABLES

9 TABLE 1 SUBBASIN SUMMARY TABLE RARE ELEMENT RESOURCES BEAR LODGE MINE PRE-FEASIBILITY STUDY Date: 2/13/14 Project Number: By: MBR Chkd: SR Design Storm 100 -Year Reccurence Interval Apprvd: REK 2-Year, 24-Hour 100-Year, 24-Hour Depth (inches) Depth (inches) Storm Distribution II Subbasin ID Subbasin Area (ft 2 ) Subbasin Area (acres) Subbasin Area (sq mile) CN = 65 CN = 86 Woods-Grass Combo HSG B Fair Cover (acres) Newly Graded Areas HSG B (acres) Composite SCS Curve No. S = CN Unit Runoff Q (in) Runoff Volume (ac-ft) Runoff Volume (ft 3 ) Pt S 2,560, CN = ,252 Pt E 1,388, CN = ,710 Pt NE 1,911, CN = ,769 Pt N 961, CN = ,650 WRF 1 4,551, CN = ,258 WRF 2 6,262, CN = ,805 WRF 3 9,221, CN = ,436,976 BC 1 13,822, CN = ,036 BC 2 6,455, CN = ,472 Pd N 7,416, CN = ,955 Pd S 3,653, CN = ,729 HR 1 3,870, CN = ,954 HR 2 2,328, CN = ,276 WT 1 3,434, CN = ,423 PLNT 1,964, CN = ,188 Pit I 9,889, CN = ,541,008 J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm Page 1 of 1 Golder Associates 2/13/2014

10 TABLE 2 BASIN TIME OF CONCENTRATION CALCULATIONS RARE ELEMENT RESOURCES BEAR LODGE MINE PRE-FEASIBILITY STUDY Project Number: Date: 2/13/14 By: MBR Chkd: SR Apprvd: REK Subbasin ID Subbasin Area (sq mile) Composite Curve Number Total Lag (0.6*Tc) (min) Total Travel Time (min) Type of Flow Length Slope (ft/ft) Flow Segment 1 Flow Segment 2 Typical Hydraulic Roughness Condition (1) Radius (Channel Only) Travel Time (min) Type of Flow Length Slope (ft/ft) Roughness Condition (1) Typical Hydraulic Radius (Channel Only) Pt S Sheet H Range 4.4 Shallow U Unpaved 0.7 Pt E Sheet H Range 4.8 Shallow U Unpaved 2.8 Pt NE Sheet H Range 5.2 Shallow U Unpaved 2.2 Pt N Sheet H Range 5.5 Shallow U Unpaved 0.6 WRF Sheet A Smooth 2.4 Shallow U Unpaved 6.3 WRF Sheet A Smooth 2.4 Shallow U Unpaved 4.1 WRF Sheet A Smooth 2.4 Shallow U Unpaved 6.3 BC Sheet H Range 6.2 Shallow U Unpaved 2.3 BC Sheet H Range 5.4 Shallow U Unpaved 2.7 Pd N Sheet H Range 6.9 Shallow U Unpaved 3.8 Pd S Sheet H Range 6.0 Shallow U Unpaved 5.0 HR Sheet H Range 5.7 Shallow U Unpaved 1.4 HR Sheet H Range 5.7 Shallow U Unpaved 1.5 WT Sheet H Range 5.8 Shallow U Unpaved 0.8 Notes: (1) Refer to Attachment A for Roughness Condition descriptions and Tc Coeffiecients. (2) PLNT and Pit I Subbasins times of concentration assumed to be 10 min Travel Time (min) J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm Page 1 of 2 Golder Associates 2/13/2014

11 TABLE 2 BASIN TIME OF CONCENTRATION CALCULATIONS RARE ELEMENT RESOURCES BEAR LODGE MINE PRE-FEASIBILITY ST Project Number: Date: 2/13/14 By: MBR Chkd: SR Apprvd: REK Subbasin ID Subbasin Area (sq mile) Composite Curve Number Pt S Pt E Pt NE Pt N WRF WRF WRF BC BC Pd N Pd S HR HR WT Type of Flow Length Slope (ft/ft) Flow Segment 3 Flow Segment 4 Typical Hydraulic Roughness Condition (1) Radius (Channel Only) Travel Time (min) Type of Flow Length Slope (ft/ft) Roughness Condition (1) Typical Hydraulic Radius (Channel Only) Channel R Riprap Channel Z Mtn. Stream Channel R Riprap Channel E Earth-lined Shallow U Unpaved 0.4 Channel R Riprap Shallow U Unpaved 2.6 Channel R Riprap Shallow U Unpaved 0.4 Channel R Riprap Channel Z Mtn. Stream Channel R Riprap Channel Z Mtn. Stream Channel R Riprap Channel Z Mtn. Stream Channel R Riprap Channel Z Mtn. Stream Channel Z Mtn. Stream Channel Z Mtn. Stream Channel Z Mtn. Stream Channel R Riprap Channel Z Mtn. Stream Channel R Riprap Notes: (1) Refer to Attachment A for Roughness Condition descriptions and Tc Coeffiecients. (2) PLNT, Pit I, and Pit II Subbasins times of concentration assumed to be 10 min Travel Time (min) J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm Page 2 of 2 Golder Associates 2/13/2014

12 TABLE 3 FLOW RESULTS FROM HEC-HMS RARE ELEMENT RESOURCES BEAR LODGE MINE PRE-FEASIBILITY STUDY Project Number: Date: 2/13/14 By: MBR Chkd: SR Apprvd: REK HEC-HMS Basin Model: Bear Lodge Rev E HEC-HMS Met. Model: 100-year 6-hour HEC-HMS Control Specs: 36-hour 5-min HEC-HMS filepath: J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\hec-hms\bearlodge_pre_feas_reve Drainage Peak Total Hydrologic Area Discharge Time of Volume Element (sq mile) (cfs) Peak (ac-ft) BC Jun2525, 01: Pt-S Jun2525, 01:00 3 R_Pt-E Jun2525, 01:00 3 Pt NE Jun2525, 01: Pt E Jun2525, 01: Junction-Pt Jun2525, 01: R_BC Jun2525, 01: J_BC Jun2525, 01: R_BC Jun2525, 01: BC Jun2525, 01: J_BC Jun2525, 01:00 31 Sink-BC Jun2525, 01:00 31 Pit I Jun2525, 00: Pt N Jun2525, 00: Sink-Pit Jun2525, 00: Pd-N Jun2525, 01: Pd-S Jun2525, 01: Sink Jun2525, 01: WT Jun2525, 01: R_WT Jun2525, 01: HR Jun2525, 01: R_HR Jun2525, 01: HR Jun2525, 01: Sink Jun2525, 01: WRF Jun2525, 00: Pond Jun2525, 00: WRF Jun2525, 00: Pond Jun2525, 00: PLNT Jun2525, 00:55 7 Sink Jun2525, 00:55 7 WRF Jun2525, 01:00 33 Pond Jun2525, 01:00 33 Page 1 of 1 Golder Associates J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm 2/13/2014

13 TABLE 3A 10-year 24-hour FLOW RESULTS FROM HEC-HMS RARE ELEMENT RESOURCES BEAR LODGE MINE PRE-FEASIBILITY STUDY Project Number: Date: 2/13/14 By: MBR Chkd: SR Apprvd: REK HEC-HMS Basin Model: Bear Lodge Rev D HEC-HMS Met. Model: 10-year 24-hour HEC-HMS Control Specs: 36-hour 5-min HEC-HMS filepath: J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\hec-hms\bearlodge_pre_feas_revd Drainage Peak Total Hydrologic Area Discharge Time of Volume Element (sq mile) (cfs) Peak (ac-ft) BC Jun2525, 01: Pt-S Jun2525, 01: R_Pt-E Jun2525, 01: Pt NE Jun2525, 01: Pt E Jun2525, 01: Junction-Pt Jun2525, 01: R_BC Jun2525, 01: J_BC Jun2525, 01:05 19 R_BC Jun2525, 01:05 19 BC Jun2525, 01: J_BC Jun2525, 01: Sink-BC Jun2525, 01: Pit I Jun2525, 00: Pt N Jun2525, 00: Sink-Pit Jun2525, 00: Pd-N Jun2525, 01: Pd-S Jun2525, 01: Sink Jun2525, 01: WT Jun2525, 01: R_WT Jun2525, 01: HR Jun2525, 01: R_HR Jun2525, 01: HR Jun2525, 01: Sink Jun2525, 01: WRF Jun2525, 00: Pond Jun2525, 00: WRF Jun2525, 00: Pond Jun2525, 00: PLNT Jun2525, 00: Sink Jun2525, 00: WRF Jun2525, 01: Pond Jun2525, 01: Page 1 of 1 Golder Associates J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm 2/13/2014

14 Table 4 Channel Hydraulic Calculations RARE ELEMENT RESOURCES Date: 12/6/13 BEAR LODGE MINE PRE-FEASIBILITY STUDY By: AMS PROJECT NO.: Chkd: MBR Apprvd: RP Channel Design Geometry Channel Roughness Parameters Hydraulic Calculations Channel Evaluations Q100 from HEC-HMS (cfs) HEC HMS Element ID for Q Approximate Channel Length Bed Slope (ft/ft) Left Side Slope (H:1V) Right Side Slope (H:1V) Bottom Width Minimum Channel Depth Design Channel Reach Designation Lining WRF WRF R Riprap WRF 2a WRF R Riprap WRF 2b WRF R Riprap WRF WRF R Riprap WRF DIV W 36.6 Pt NE R Riprap PIT DIV S 48.5 Pt-S R Riprap PIT DIV N WT R Riprap PIT DIV N R_HR R Riprap BC DIV U J_BC R Riprap BC DIV L J_BC R Riprap PD-N PD-N R Riprap PD-S 70.4 PD-S R Riprap < 1/2 Vel. Head indicates that the remaining freeboard is less than 1/2 the velocity head (V 2 /2g) suggesting water may splash out. Warning: VxD>9 indicates that the velocity times the depth is greater than 9 ft 2 /sec, which is undesirable and may be un Unstable V indicates that calculated velocity exceeds the recommended maximum for the lining material. Unstable T indicates that calculated shear stress exceeds the recommended maximum for the lining material. Mannings 'n' for Capacity (Depth Calculation) Mannings 'n' for Stability (Velocity Calculation) Maximum Velocity (ft/sec) Maximum Normal Flow Depth Froude Number Normal Depth Shear Stress (lb/ft 2 ) Stream Power (W/m 2 ) Top Width of Flow Top Width of Channel Available Freeboard J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev D v2.xlsm Page 7 of 7 Golder Associates 1/14/2014

15 Table 5a U.S. Corps of Engineers (mild) Method Riprap Size Calculation Riprap Channel Evaluation Date: 12/6/13 Bear Lodge Mine By: AMS PROJECT NO.: Chkd: MBR Apprvd: RP Reach Designation Design Flow Q (cfs) Normal Flow Depth d Depth Averaged Velocity V (ft/s) Velocity Distribution Coefficient C V Channel Side Slopes Correction K 1 Calculated Particle Size D 30 Riprap Size D 50 (in) Recommended Riprap D 50 (inches) BC DIV U BC DIV L USACE Paper EM , 6/30/94 D = S USACE Method Riprap Calculations for Mild Riprap (Bed Slopes <2%) γ C C C d w 30 f s V T γ s γ w K1gd Inputs below as determined in EM , 6/30/ S f : Minimum safety factor of 1.1 for moderate debris impact 0.3 C s : Value of 0.30 for angular rock 165 γs: Density of solids (pcf) 2.2 Cg: Gradation Coefficient (D 85 /D 15 ) 2.0 T: Riprap Thickness (x D 50 ) C T : Correction for thickness > 1.5 * D 50 Note: A C V of 1.25 should be used downstream of concrete channels due to the difference in velocity profiles Riprap D50 determined as recommended in EM , 6/30/94 V 2.5 D 1 3 D = D D15 Page 1 of 2 Golder Associates J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge Riprap Rev D.xlsm 1/14/2014

16 Table 5 U.S. Corps of Engineers (Steep) Method Riprap Size Calculation Riprap Channel Evaluation Date: 12/6/13 Bear Lodge Mine By: AMS PROJECT NO.: Chkd: MBR Apprvd: RP Reach Designation Design Flow Q (cfs) USACE Method Riprap Calculations for Steep Riprap (Bed Slopes >2% but <20%) Normal Flow Depth d Unit Flow (ft 2 /sec) Flow Concentration Factor Calculated Particle Size D 30 Riprap Size D 50 (inches) Recommended Riprap D 50 (inches) WRF WRF 2a WRF 2b WRF WRF DIV W PIT DIV S PIT DIV N PIT DIV N PD-N PD-S * Reach HR-U is consumed by the Reserve Pit USACE Paper EM , 6/30/ S q D 30 = 1 3 g Inputs below as determined in EM , 6/30/ Cg: Gradation Coefficient (D 85 /D 15 ) Riprap D50 determined as recommended in EM , 6/30/94 D 1 3 D = D D Flow Concentration Factor (1.25 from USACE steep riprap method) Page 2 of 2 Golder Associates J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge Riprap Rev D.xlsm 1/14/2014

17 FIGURE

18 LEGEND Pd N WRF S WRF 1 Pt NE NOTES RARE ELEMENT RESOURCES BEAR LODGE PROJECT, BULL HILL MINE CROOK COUNTY, WYOMING PRE-FEASABILITY WATERSHED MANAGEMENT PLAN FIGURE 1

19 ATTACHMENT A HEC-HMS MODEL PARAMETERS

20 Attachment A HEC-HMS Screen Captures and Inputs HEC-HMS Basin Model Schematic (Mineable Scenario) Subbasin Sub Basin Area Area (mi 2 ) Subbasin Loss SCS Curve Number Initial Abstraction Curve (in) Number Impervious (%) Subbasin Lag Time (hr) %Time %Rainfall BC BC BC Pt-S Pt-S 65 0 Pt-S Pt NE Pt NE 65 0 Pt NE Pt E Pt E 65 0 Pt E BC BC BC Pit I Pit I 86 0 Pit I Pt N Pt N 65 0 Pt N Pd-N Pd-N 66 0 Pd-N Pd-S Pd-S 65 0 Pd-S WT WT WT HR HR HR HR HR HR WRF WRF WRF WRF WRF WRF PLNT PLNT 86 0 PLNT WRF WRF WRF Length Routing Kinematic Wave Channel Slope (ft/ft) Manning's n subreaches Shape Diameter Width Transform SCS Unit Hydrograph Side Slope (xh:1v) Reach R_Pt-E Trapezoid R_BC Trapezoid 10 3 R_BC Trapezoid 10 3 R_WT Trapezoid 10 5 R_HR Trapezoid 50 9 Dimensionless S-Graph J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm Page 1 of 1 Golder Associates, Inc. 2/13/2014

21 ATTACHMENT B HY8 CULVERT SIZING OUTPUT

22 December 2013 Attachment B HY-8 Culvert Analysis Culvert D1 Inputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

23 December 2013 Attachment B HY-8 Culvert Analysis Culvert D1 Outputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

24 December 2013 Attachment B HY-8 Culvert Analysis Culvert D1 Outputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

25 December 2013 Attachment B HY-8 Culvert Analysis Culvert D1 Outputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

26 December 2013 Attachment B HY-8 Culvert Analysis Culvert D2 Inputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

27 December 2013 Attachment B HY-8 Culvert Analysis Culvert D2 Outputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

28 December 2013 Attachment B HY-8 Culvert Analysis Culvert D2 Outputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

29 December 2013 Attachment B HY-8 Culvert Analysis Culvert D2 Outputs j:\11jobs\ bear lodge mine\surface water\h&h calculations\hy8\attachment b hy-8 rev d.docx

30 ATTACHMENT C PIT DEWATERING SEDIMENT POND SIZING

31 February Table C1: Sediment Pond Sizing Summary Catchment Area (ac) 10-Year Event Volume (ac-ft) 1 Sediment Storage Volume (ac-ft) 2 Total Pond Volume (ac-ft) 3 Sediment Pond Waste Rock Facility Pond Pond Pond Pit Pond Environmental Flows Pit Dewatering PUG Plant PUG Plant Pond Notes: 1. In accordance with the Wyoming Department of Environmental Quality Water Quality Rules and Regulations, Chapter 11, Section 31, the sediment ponds are sized to accommodate the 10-year 24- hour runoff event. The design storm event was modeled using the Hydrologic Engineering Center's HEC-HMS program. Additionally, the ponds must be sized to accommodate the expected sediment 2. The annual volume of sediment generated was assumed to be equal to one inch of runoff from the entire catchment area. This corresponds to 3,630 ft 3 /acre. 3. Total pond volume represents a neatline volume and does not include the required freeboard. J:\11JOBS\ Bear Lodge Mine\Surface Water\H&H calculations\bear Lodge H&H v4.11rev E.xlsm

32 December 2013 Attachment C Settling Velocity Calculations Calculation of the settling velocity u of a single particle: natural sediment or spherical Janwillem Rouweler; HAS University of Applied Sciences; N input cel: yellow calculation cel: blue INPUT: Acceleration of gravity g = 9.81 m/s 2 usually g = 9.81 m/s 2 Density of particle ρ PARTICLE = ρ P = 1100 kg/m3 Diameter of particle d = meter (Be Aware: 1 mm = m) Assume Fine sand Density of fluid ρ FLUID = ρ F = 1000 kg/m3 usually water ρ F = 1000 kg/m 3 Viscosity of fluid η FLUID = η F = Pa s usually water η F = Pa s "Dimensionless particle diameter d * "= Natural particles (Song Zhiyao): Settling velocity u = m/s Re = ρ F *u*d/η F = 5.76E ft/s Spherical particles (Guo): Settling velocity u = m/s Re = ρ F *u*d/η F = 7.57E ft/s V S = 0.01 ft/s Settling velocity for the design particle size chosen Q = 1.11 cfs 500 gpm Discharge rate measured in cubic feet per second A S = 177 sq. ft. Minimum surface are for trapping soil particles of a certain size J:\11JOBS\ Bear Lodge Mine\Surface Water\November 2013\Pit Dewatering Pond\SedBasin_1.xls

33 December 2013 Attachment C Pond Sizing Calculations Influent Parameters m 3 /day Flow gpd gpm 500 Influent TSS mg/l 1500 Effluent TSS mg/l 35 Sedimentation Basin Mass of Sludge without Anaerobic Decomposition kg/yr 1,457,391 Ratio of Fixed Solids to VSS Volatile Solids kg/yr - Fixed Solids kg/yr 1,457,391 Volatile Solids Reduction % 0% Sludge Accumulation years 1 VSS decomposition years 1 yr 1 kg/yr - Total SS yr 1 yr 1 1,457,391 Total Solid yr 1 kg 1,457,391 Detention Time days 2 m 3 5,451 Volume gallons 1,440,000 ac-ft 4.4 Lagoon Depth m 1.00 m 2 5,451 Surface Area ft2 58,653 Mass of Accumulated Sludge / Area kg/m Density of Sludge kg/m Average Compaction % 15% Sludge Bank Depth m 1.68 m 2.68 Total Lagoon Depth ft 8.80 Length to width ratio 3.0 ft Length m ft Width m 42.6 Laminar Velocity ft/s Laminar Velocity Contingency Adjusted Laminar Velocity ft/s Settling Velocity ft/s Settling Velocity - Adjusted Laminar Velocity ft/s Water Storage ac-ft 4.4 Sediment Storage ac-ft 7.4 Total Required Storage ac-ft 11.8 J:\11JOBS\ Bear Lodge Mine\Surface Water\November 2013\Pit Dewatering Pond\SedBasin_1.xls