Cienega Cr Watershed Hydrologic Evaluation of Proposed Hermosa Mine Water Treatment Plant (WTP2) Discharge
Presentation to PARA November 12, 2020 Sonoita Cr Watershed
Laurel Lacher, PhD, RG, Lacher Hydrologic Consulting, Tucson, AZ
Bob Prucha, PhD, PE, Integrated Hydro Systems, LLC, Boulder, CO Study Commissioned by PARA
• Purpose of Study: − To evaluate potential hydrologic impacts of South32’s proposed discharge of treated water from the Hermosa Project to Harshaw Creek as described in August 2020 AZPDES and APP applications. South32’s Proposed Action
• South32 (parent company to Arizona Minerals, Inc.) proposes dewatering of Hermosa Project area ~ 5 miles south of the Town of Patagonia to facilitate underground mining. 1) Taylor Deposit (zinc, lead, silver) 2) Clark Deposit (zinc, manganese, silver)
Initial dewatering rate up to 4500 gpm Treated water discharged to Harshaw Cr. Hermosa Project
Modified from Clear Creek Assoc., Aug 2020, APP Significant Amend. Applic P-512235, fig. 1. Motivating Factors for PARA
Existing Flood Potential on Harshaw Creek and in Town of Patagonia South32’s conclusion of no surface water impact in Sonoita Cr. History of Flooding in Patagonia
2017 Watershed Management Plan
Perennial flows along Sonoita and lower parts of tributaries shown Streamflow at Patagonia-Sonoita Cr. Preserve (m3/s) Recent Harshaw Elevated Baseflows – amplify flood potential Creek Flooding Data courtesy of The Nature Conservancy
Sonoita Cr Watershed Precipitation (mm) Sonoita Cr Watershed Precipitation (mm)
8/7/16-8/12/16 7/15/17-7/24/17
Harshaw Creek Flows Harshaw Creek Flows July 22, 2017 August 9, 2016
Key Points • Monsoonal storms leading to Discharge on Harshaw Cr relatively typical annual monsoon storm events • Preceding storms increase surface saturation and runoff South32 Findings (presented July 21-22, 2020) Literature Review Documents Reviewed Proposed New Discharge from WTP2 to Harshaw Creek Study Objectives
1. Evaluate effects of 4500 gpm mine dewatering discharge from WTP2 on: • Streamflow − Harshaw Cr − Sonoita Cr • Conveyance of Mine Discharge − Natural regime PLUS mine dewatering − Along Harshaw Cr − Through town of Patagonia • Groundwater − Groundwater-dependent ecosystems − Aquifer storage changes
2. Assess baseline hydrologic conditions and controlling factors
3. Develop a robust numerical model of Sonoita Cr watershed applicable to other problems Integrated Modeling
MIKESHE by DHI
https://www.mikepoweredbydhi.com/products/mike-she MIKESHE / MIKEHydro flexible process descriptions
• Choice of spatial and temporal scales (depends on processes): • Groundwater (days to years) • Surface water (seconds to hours) • Unsaturated flow (seconds to years)
• Process time scales independent and automatically controlled
• Choice of processes to include in model
• Choice of simple to complex solutions
• Groundwater flow virtually identical to MODFLOW.
● Green and Ampt • FEMA‐approved fully hydrodynamic, surface water hydraulic model MIKESHE Model Development Approach
Distributed NLDAS Meterological Data USGS Data (3 hourly) ADWR Data (Geology and -Air temp Wells/Water levels) -Precip -PET
Soil Vegetation Model Landuse Development
Snow Depths Preliminary Stream Q (Phase 1) Heads Updated parameters, Time- varying distributed Recharge & AET Integrated Model ET Soil Moisture Calibration Water Quality (2000 to 2020)
Preliminary Predictive Local Scale Uncertainty Scenarios Regional Model (Phase 2) (Phase 1) Analysis (Phase 2) Model Scenarios Hermosa Mine Refine Calibration (More accurate/improved resolution) (account for WTP Discharge uncertain inputs) (4500 gpm) Conceptual Model Springs – can occur at Generalized Conceptual Basin Flow Model faults when upgradient GW forced to surface. Alluvial ‘Valley’ Fill (along Sonoita 10 m Creek) - High permeability gravel/sand matrix interbedded with clay/silt lenses controls ‘bank’ storage. Clays/silts limit vertical flows and surface infiltration
Relatively thin veneerUnweathered of Bedrockhigh 790 m permeability colluvium (3 to 6 m) supports vegetation.
Unweathered Bedrock Weathered Bedrock zone – Most productive wells fractured, higher permeability than screened in alluvium; underlying unweathered bedrock. some enhanced by Perches GW in overlying colluvium faulting – critical control on streamflow.
Fault – impedes flow across Unweathered Bedrock –low it. Heads higher on permeability, isotropic unfractured. upgradient side. Many wells screened in bedrock Conceptualization of Unsaturated Zone Flow
Variable soil types Strongly control ET dynamics, infiltration & recharge to aquifer Saturation increases above clay layers Influences infiltration and recharge to groundwater Unsaturated Zone Moisture Deficit draws water Groundwater Recharge UPWARD from water table Response to stream stage (capillary draw). Macropores rapid recharge Shallow, low Perched Flow – above shallow Surface Water Runoff permeability bedrock bedrock Mechanisms
Shallow bedrock • Causes rapid surface saturation, increasing runoff • True in many areas
Low permeability soils with deeper GW table & bedrock Shallow groundwater table • Runoff occurs as ‘Hortonian Flow’ • Limits aquifer storage (i.e., rainfall rate exceeds infiltration capacity). capacity • Unlikely in most storms • “Rejects” infiltrating water, low permeability increasing runoff bedrock Evidence for Runoff Mechanism Surface water discharge appears strongly controlled by shallow GW table (locally-perched or connected to regional aquifer) for several reasons: • Reported range of soil permeability doesn’t produce peaky discharge (i.e., Hortonian runoff) • Aquifer storage effects apparent in surface discharge at Preserve gage • Relatively shallow GW beneath town/Sonoita Cr • Perennial flow along lower reaches of most tributaries and downstream of Town where shallow bedrock forces GW to surface. (eg, TNC preserve)
Shallow groundwater Shallow bedrock
low permeability bedrock Streamflow at Precipitation at Patagonia-Sonoita Cr Preserve*
Delayed stream flow response
* Data courtesy of The Nature Conservancy REGIONAL Model Setup/Assumptions Model Domain, Discretization, and Hydraulic Network
• 500 m grid cells Mt Wrightson • Entire Sonoita Cr watershed Cienega Cr Watershed • Sonoita Creek and main tributaries • Patagonia Lake Patagonia Town of Lake Patagonia
Proposed WTP2 Discharge Location
Sonoita Cr Watershed Climate Data NLDAS Zones (11.4 km x 13.8 km spacing)
• NASA’s National Land Data Acquisition System (NLDAS) data • Hourly Rainfall, Potential Evapotranspiration (PET), and Air Temperature (2000 through 2020) Can supplement with • Benefits of NLDAS dataset: local weather station data • spatially distributed (~11.4 x 13.8 km grid) • no data gaps • hourly consistency between rain, PET and air temperature. These data ‘drive’ the hydrologic and snowmelt response. Precipitation (mm/day) • Elevation lapse rates adjust rain and air temp account for orographic effects.
SNOWMELT PARAMETERS • Melting Temperature – 0º C (uniform) Hourly Air Temp (C) Potential ET • Degree Day Coeff – 4 mm/C/day (mm/day) • Maximum Wet Snow Fraction – 0.1 • Thermal melting (from rain heat on snow) included – Melt Coeff – 0.131/C B HermosaMine ran c h 17 MIKEHYDRO_HermosaMine_CrossSections
Bran MIKEHYDRO_HermosaMine_Branches Unsaturated ch 5 MSHEmodel_Sonoita B r an ch Faults_MSHEcombinedREVISED 19 Zone Places (Outline)
Bran Cnty Bnds (detailed, named) ch 2 Bran ch 18 SSURGO (0 to 100 cm) • USDA - SSURGO Soil Ksat values x1e-6 m/s 0 - 4.2 Survey data 4.3 - 9 B ranch 20 9.1 - 16.3 • Similar to AZGS 16.4 - 26.9 27 - 66.1 UV83 B Branch ra 24 66.2 - 189.1 Surficial Geology and 4 n c 1 B h h c ra 2 189.2 - 425 n n 2 a r c h supported by well logs B 6 UV82
3 • Saturated hydraulic h 2 Santa Cruz Branc Branch ch 12 2 an 1 conductivity values Br 13 ch 6 n 1 H a h a shown for top 100 cm. r rs c ha B n w ra C Branch B r 4 eek • These data converted into AlumGulch B ra n c h 8 MIKESHE soil types. 9 h c n S a on r o B itaCr eek
• Assumed uniform to B ran ch higher elevation of 10 11 h c an either groundwater table Br or bedrock surface. UV289 §¨¦19 ± 02461 Miles Clays present in Harshaw Creek MUD CRACKS and Valley Alluvium
Middle Harshaw Cr.
(Nassereddin, 1967) 55‐536795 !< ") Hermosa Project Borehole Logs 8 h nc a ") Br
Alu mG !< u ") lc! BH-14 #* ") Harshaw Creek BH-01 #* BH-12 #* #* ") TP-02 Newfield_Mine_boreholes_pits ") ") #* #* ME TP-25 BH-11 BH-10#* ") -520.7 - -480.1 #* TP-07 #* #* #* ") -480.0 - -100.0 #* BH-09 -99.9 - -50.0 TP-53 #* BH-16 ") #* #* ") -49.9 - -10.0 TP-06 ") ") BH-15 ") -9.9 - -5.0 #* ") -4.9 - -3.0 TP-08 #* -2.9 - 3.0 #* ") 3.1 - 5.0 ") 5.1 - 10.0 ") ") 10.1 - 50.0 ") 50.1 - 100.0 ") 100.1 - 390.4 MIKEHYDRO_HermosaMine_CrossSections MIKEHYDRO_HermosaMine_Branches ") GWmodelboundary Streams_all 00.1 0.2 0.4 0.6 Cnty Bnds (detailed, named) Miles Most logs show soils overlying bedrock have significant clays & silts – even within Harshaw Creek. Looking down Sonoita Creek toward 3D Lithologic Model – Deposits Overlying Bedrock Patagonia Patagonia Borehole Lithology from ADWR’s Well55 Registry Driller’s Logs Patagonia Lake Lithologic Color Legend Increasing Permeability Bedrock Patagonia Sonoita Cr Clays Silts Sands Gravels WTP2 Saturated Zone 4 model layers 10 m Layers 1 & 2 (alluvium & weathered bedrock) Unweathered Bedrock 790 m Layer 3 – Weathered Bedrock Unweathered Bedrock Layer 4 – Competent Bedrock Depths to bedrock increase rapidly into Unconsolidated Material Thickness - Isopach Cienega Creek watershed to north B ranc h 17 Thickness data shows Bran ch5 3 B 20 r 0 • 100s of feet thick from an ch 19 48 Patagonia to ~7.5 miles north 00 Br 1 an 6 ch 2 500 0 0 Bra n 8 ch 0 along Sonoita Creek 18 0 4 0 0 • Shallows at/south of 350 447 B Patagonia, along Sonoita (~20- ranch 20 30 feet) B Branch ra 24 • Harshaw depth variable (~150 4 n 1 B c 83 h 82 UV h r a 2 UV c n n 2 a c r h to 10 feet) B 6 HermosaMine ADWR well log locations Santa Cruz MIKEHYDRO_HermosaMine_CrossSections 3 Branch 2 Bran MIKEHYDRO_HermosaMine_Branches 500 ch2 ch 12 1 an Br Cnty Bnds (detailed, named) Ha rs MSHEmodel_Sonoita 3 h Cochise 1 aw ch 6 C n 1 Patagonia bedrock depth (ft) Arizona State Depth to Bedrock re a h e r c k B n -7 - 2.5 a r Branch 4 – borehole location (ft) B 2.6 - 5 5.1 - 10 10.1 - 15 AlumGulch 15.1 - 20 B ra 20.1 - 25 k n e e c aCr h 25.1 - 50 Assumed thickness ~3 m noit 9 So 50.1 - 100 8 h c hilltop areas, and ~6 m n 100.1 - 250 a r B 250.1 - 500 B ran ch 40 500.1 - 1,000 along drainages (where 10 0 400 8 1,000.1 - 4,928.5 00 11 2004 Places (Outline) data lacking) h 16 c 0 an 0 Br Faults_MSHEcombinedREVISED #* CombinedBedrockDEPTH 1900 981 AZ depth to bedrock (ft) 02461 540 ") AZ bedrock control point Miles c rhyolite o s Saturated Zone n an sand g l B a o r nch ds 1 m 7 r Hydraulic Properties h t B r e o g r an y ch 5 ne h r r o a a y li t t n o conglomerate e B e r o l an g i c d t h conglomerate r e 19 a i o v r e i Br l t anc e h 2 sa Branc c n h d 18 Utilized hydraulic o sto n ne g r s h te a l a ra properties (conductivity n o y me n lo d m o ng e d co li s e t s i c e and storage) from t r o t e B o l a n r g anch 20 ve n t lo ra g e m e g modeling associated with r e a ra rh schist a n n te y d o o Rosemont Mine EIS e d l ravel B g i Branch it s o ra 24 e i n t r c 83 e h 82 s UV B i a s t 2 UV ra e 2 n an n d c s ds 4 h l t 6 o 1 n e ton h e conglomerate Refinement of hydraulic c v n ra a s e r Santa Cruz a c B n sa o sandstone g 3 d n h2 s g Branc Br t ndston l property distributions anch o o nch 12 2 n m ra 1 e B er Patagonia at Har a e e guided by AZGS surficial sh nd 3 aw 1 6 C h 1 e e c t re n h a ek site a c r n r a B a geologic zones dacite r e n Branch B m d 4 lo es g i n te o c AlumGulch andesite ree k g aC r it a no B B o n r S a ra nc n o h c Cochise 9 h d 8 11 h r i h o c n y a o r r l i B it t HermosaMine e e Br an s MIKEHYDRO_HermosaMine_CrossSections ch rhyolite 10 a gravel conglomerate n e MIKEHYDRO_HermosaMine_Branches c on d st ite o nd Cnty Bnds (detailed, named) s a g s n to conglomerate r g MSHEmodel_Sonoita a gran l n o e n n Places (Outline) e me to o es d lim Faults_MSHEcombinedREVISED i r o 02461 a #* CombinedBedrockDEPTH granodiorite r conglomerate t Miles i e andesite t e granodiorite rhyolite Faults and Springs Faults can either impede flow across OR facilitate flow along them. MIKESHE modeling assumed they all impede flow. Further evaluation is needed. Groundwater flow could be enhanced along the Harshaw Creek/Santa Rita Fault zone or similar faults. Patagonia Harshaw Creek/Santa Rita Fault zone Fault map by Drewes, 1996 MIKEHYDRO_HermosaMine_CrossSections MIKEHYDRO_HermosaMine_Branches B ran c h 17 2014 Existing GWmodelboundary us_140evt_1 Branch Vegetation EVT_PHYS 5 Agricultural B r an Barren ch 19 UV83 Types Conifer Conifer-Hardwood Br anch 2 Developed B ran ch Developed-High Intensity 18 Developed-Low Intensity Developed-Medium Intensity Leaf Area Index (LAI) from Developed-Roads Exotic Herbaceous Bra 8-day MODIS satellite Exotic Tree-Shrub nch 20 Grassland (from 2000 to 2020) drives Open Water Quarries-Strip Mines-Gravel Pits B Branch 2 Riparian ra 4 4 n Actual ET. Consistent with c 1 B r h h a Shrubland c 2 n n 2 a c Sparsely Vegetated r h wet/dry climate periods. B 6 Streams_all k Cnty Bnds (detailed, named) e e Santa Cruz r C a t 3 i ch 2 o Bran Branch 12 2 ch on 1 !< an S 3 main types: Br Ha !< Patagoniars 13 ha h w c 6 C • Conifer n 1 r a ee r h k c !< B n ra Branch 4 • Shrubland B • Grassland !< AlumGulch !< B ra n c 82 h !< UV 9 8 ch !< !< n a r ! 289 !< UV !< Source: Esri, LAI RD Maxar, [()] [millimeter] 220 1.0 200 LAI 180 Depth Root 0.0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 [s ] Boundary Conditions Includes Patagonia Community Water Groundwater Pumping System Pumping by year (2 wells) Mt Wrightson Assumed 0.5 ac-ft/yr net pumping from all ADWR Wells. Patagonia 14 80 Groundwater Level (m) 1 1 7 6 0 0 6 2 980 - 1060 Bran 4 0 0 ch Groundwater 1 1 1440 7 1061 - 1140 B ra Groundwater Levelnch 5 Surface 1141 - 1220 1221 - 1320 Level Data B and Flow Directions ra n 40 1 ch 4 1321 - 1420 7 1 1 4 9 0 1421 - 1500 1 Br 78 an 1501 - 1580 0 ch 2 Bran 0 1581 - 1660 ch 42 18 1 1 1661 - 1760 1 8 7 4 ADWR GWSI and Well-55 6 0 1 0 15 1761 - 1880 7 1 00 20 4 15 16 0 20 HermosaMine 80 0 Registry data used to 0 64 MIKEHYDRO_HermosaMine_CrossSections 1620 1 00 16 158 60 Bra 0 15 nch 20 0 MIKEHYDRO_HermosaMine_Branches create a time-averaged 20 50 1540 15 1 0 1420 0 MSHEmodel_Sonoita 8 1 1500 4 0 54 1 6 1 48 14 0 Faults_MSHEcombinedREVISED groundwater 4 0 4 1 0 20 2 15 Places (Outline) 4 B 0 Branch 1 ra 24 0 n ‘potentiometric’ surface 4 c 83 Cnty Bnds (detailed, named) 1 0 h 82 UV B 8 40 2 UV 5 3 1 r 2 a 1 0 n 6 0 c 3 8 4 h 1 map. 2 6 0 1 4 1 0 2 0 34 1 0 h 1 2 c 0 1 n 32 0 a 1 24 r 0 1 1 Santa Cruz B 130 2 4 23 0 ranc h B 80 B ranch 15 nch 12 2 Initial condition for the a 0 1 Br 4 3 1 HPatagoniaa rs 1 h 5 Cochise integrated model. 3 a 6 1 6 w 0 h 1 C c re n h ek a c r n 1 a 2 B 1200 r 20 Bran 1 B 0 ch 4 2 26 20 1 0 Transient water level data 118 60 11 are used as calibration AlumGulch 140 1 ree k aC 11 it 80 ono B data in the model. S ra nc 1120 h 9 8 h 0 c 12 n 1 a r B 1100 B ra 1 1 n 46 4 c 1 0 h 4 1 6 1 0 48 0 4 0 0 1560 1 1520 1 c h ran 0 1 B 6 62 00 0 0 16 1 1 20 0 Contour interval 20 m 5 6 8 8 1 4 1 1 0 54 0 1 64 0 024680 1 5 1 1 0 4 10 1 60 Miles 0 6 6 0 ± HermosaMine B ran MIKEHYDRO_HermosaMine_CrossSections c h 17 Depth to MIKEHYDRO_HermosaMine_Branches Br MSHEmodel_Sonoita anch5 Faults_MSHEcombinedREVISED B r an Places (Outline) ch Groundwater 1 9 Cnty Bnds (detailed, named) k ree aC Groundwater depth (m) Bran Sono it ch 2 B 16 - 20 ranch 20 surface: 21 - 25 26 - 30 31 - 40 B Branch 2 Shallow bedrockra 4 41 - 50 • increases in deeper 4 n 83 1 c B 82 UV h h r 2 UV 51 - 75 c a n n 2 a r c forcesh gw up 76 - 100 bedrock areas B 6 toward surface 101 - 150 • shallow along most of Santa Cruz 151 - 284 3 h 2 Branc Branch Harshaw Creek (~2 to ch 12 2 an 1 Br Ha rs ~15 m) 3 Patagoniah Cochise 1 aw ch 6 C n 1 re a h e r c k B n ra ranch4 B B Shallow groundwater limits AlumGulch B ra n surface infiltration c h 9 8 h c n a r B B ran ch Areas of greater depth to gw 10 1 1 affected by pumping and/or h c an Br geologic features 02461 Miles ± Preliminary Model Performance/Calibration Snowmelt Streamflow Groundwater Simulated Snowmelt Mount Wrightson (Should be calibrated to snow water equivalent data) mm year Simulated Actual Evapotranspiration Mt Wrightson (AET) Higher Altitudes produce more AET, mostly due to increased precipitation with elevation. Simulated Discharge – USGS Patagonia Gage (1930-1972) B r Hydro routes anc h B 6 r a HermosaMine B n ra c nc h h 2 MIKEHYDRO_HermosaMine_CrossSections 2 2 k MIKEHYDRO_HermosaMine_Branchese No active gaging stations in model e r Patagonia 1 C MSHEmodel_Sonoita n T o e y m C Faults_MSHEcombinedREVISEDn ieneg p uita Canyo a n o C area! r Places (Outline) h a s l A G kk ee Cnty Bnds (detailed, named) u ee l rr c h CC • Continuous flow record would Branch aa 12 itit oo nn oo k SS ee Cr 2 n !( yo provide critical model calibration ia n a n Stevens2 k C o oc g R k !( a Stevens1 d t e e R a !( e !( 4 r Bra P nch C data FARM n o y H n 6-4/5 a !( r a !( 5-4 s !( h C !( !( awCre e 14-5 e n 16-6 i 6 k 1 !( !( NASH M h H l c !( n ar Seasonal variations in baseflow realistic at Preserve a a sh o r 20-5!( !( a B !( w C !( !( 18-4 C MW-2 !( re !( ek !( MW-1 gage. Hourly measurements are required to confirm !( H a MW-4 ar Manual low-flow measurements C rs C h B r a r e w a e w ek n Santa Cruz 82 Patagonia- k ch UV short-term ‘storm-event’ peak flows. 1 at TNC Preserve only flow data 4 Sonoita Cr available for model period 2000-2020 Preserve Observed discharge (dots on lower plot) are from 1960s- AlumGu eek lc h Cr ita A o l on u S m USGS 09481500 G early 1970s only for comparison. Baseflows and range u l c h of peak flows are reasonable – but need actual data. eek r taC noi B So ra n ch 9 8 h c n ww T aa h a kk re r hh a e ee a R B ss tt r ii C r ee a r r oo ny aa nn kk on CC oo ee B C HH SS ee r ree CCrr a k n ch 10 ek re C aw rsh Ha C ox n k G o e ul y re ch n wC ha s Ca r t a d H l 01230.5 o Miles b m Hu ± Preliminary Simulated Transient Heads Many potential reasons for deviations: • Relatively coarse model grid a finer grid will better simulate local flows/heads • Assumed pumping (0.5 ac-ft/yr) at all wells • Variations in local geology • Faulting assumptions (some faults facilitate flow) • Water level measurements (ADWR) • Old/outdated • Influenced by pumping • Assumed screened depths • Upstream diversions (stock ponds, etc) • Upstream AG-irrigation • Legacy mining dewatering • Current/recent mining dewatering • Inaccuracy in initial heads Further calibration required Simulated vs. Observed Heads (all ADWR wells) UV82 Bra nch 17 Preliminary results – identify Bra Branch n 5 ch 19 areas needing further refinement. B ran ch 2 Bran ch 18 • Green triangles indicate B ranch 20 reasonable calibration. FortFort Huachuca B ranch 24 B r a n 4 c 1 h Br 6 h • 822 wells – multiple depths a c n n c ra h 3 B 2 2 2 c h 83 Bran Bra UV 12 nch ch 2 an 1 Br UV82 13 6 • Spatial coverage limited ch 1 n h H a c ar r n sh B ra aw Branch B Santa Cruz C 4 Cochise ree outside of main drainages k AlumGulch HermosaMine B Mean Error (m) (2000 to 2020) ra n 8 ch ") h <-50 m 9 c So n no a ") -49.9 - -25.0 ita r Cree k B ") -24.9 - -10.0 B ran ch ") -9.9 - -5.0 10 1 ") -4.9 - -5.0 1 h c an #* -4.9 - 5.0 Br ±5 m ") 5.1 - 10.0 ") 10.1 - 25.0 UV289 19 §¨¦ ") 25.1 - 50.0 ") >50 m MIKEHYDRO_HermosaMine_CrossSections MIKEHYDRO_HermosaMine_Branches MSHEmodel_Sonoita Faults_MSHEcombinedREVISED 19 ± Places (Outline) §¨¦ £¤89 02.557.51.25 Cnty Bnds (detailed, named) UV189 Miles M C a k A a e C d re n e r C re ne yo ra ard e G n TNC updated flow status k Branch Perennial Flow 1 FLOW STATUS 7 Perennial B r anch 5 A Formerly Perennial Reaches – TNC k r B e ive Regulated B e R ig r ri C ra a n C m a C ch co a o Aqueduct n a 1 ab y s 9 g B M o a o n e Effluent Dominated (May Be Formerly Perennial) u n n B t C W l e a i r r ig e n Hydro routes h C tso e c 83 n 2 k a UV Important MIKEHYDRO_HermosaMine_CrossSections Branc h 1 MIKEHYDRO_HermosaMine_Branches 8 calibration Streams_all Cnty Bnds (detailed, named) B ra n c data in lieu of h 012340.5 B 2 ran n ch 20 Miles o y n a gaging C e n i h h p c e B Bra ul nc s r h 24 o a stations G B n J l c ra h n a c r 2 4 h o 2 1 6 p h m c e n T a r 1 ia Cieneguita B on ag Santa Cruz k Canyon at e P e r 3 h2 C Branc Bra 2 a nch nch 12 ia it 2 !< ra n o 1 B go n ta o S a S P Ha M a rs !< o n h B o 4 2 n a r h anc u C k 6 w a s t n C a e 1 n B r R e t e y e e i e d a h y r r a k R i e k o a c t c a n k t e C n C a !< n n s a e H an C r y n r u n a c C on e 1 a r o B t s C o o n h n i h r i a ee y o a n w k M 1 n M o n C S 3 k o y re k l a e S e H a n k e a e C r o a r s e h r k C h a c C C H w e s a P n C r o !< s 3 y A h an n AlumGulch aw C o A H 2 y l a n u m rs a h !< T a C h G r w S e u o e 1 a R B lc n S C r h n s a a 82 a t n n a n e UV y c r h t !< B o a n C F r 9 a C 8 C r r n e u c e h r k z u h c !< n z 1 !< R 0 a R r i M v i n B e v ! a r r z o t e u S n C r iv !< a C a 289 R r C n UV S R r e i !< v u t e a e z k r Simulated Gaining and Losing Reaches General agreement between MIKESHE and Perennial stretches. Stream flows Note MIKESHE indicates Stream flows INTO aquifer gaining/losing reaches vary OUT OF aquifer (Losing reach) throughout the year (Gaining reach) M Ca A a eek Cr d Cr n e er e y r dn o a ar e G n TNC updated flow status k Branch FLOW STATUS 17 Perennial B r anch 5 A Formerly Perennial k r B e ive Regulated B e R ig r ri C ra a n C m a C ch co a o Aqueduct n a 1 ab y s 9 g B M o a o n e Effluent Dominated (May Be Formerly Perennial) u n n B t C W l e a i r r ig e n Hydro routes h C tso e c 83 n 2 k a UV MIKEHYDRO_HermosaMine_CrossSections Branc h 1 MIKEHYDRO_HermosaMine_Branches 8 Streams_all Cnty Bnds (detailed, named) B ra n c 012340.5 h B 2 ran n ch 20 Miles o y n a C e n i h h p c e l B Bra u nc s r h 24 o a B G n J l c ra h n a c r 2 4 h o 2 1 6 p h m c e n T a r 1 ia Cieneguita B on ag Santa Cruz k Canyon at e P e r h23 C Branc Bra 2 a nch nch 12 ia it 2 !< ra n o 1 B go n ta o S a S P Ha M a rs !< o n B o h 2 4 n a r h anc u C k 6 w a s t n C a e 1 n B r R e t e y e e i e d a h r y r a k R i e k o a c t c a n k t e C n C a !< n n s a e H an C r y n r u n a c C on e 1 a r o B t s C o o n h n i h r i a ee y o a n w k M 1 n M o n C S 3 k o y re k l a e S e H a n k e a e C a r o r s e h r k h c C C C H aw e s a P n C r o !< s 3 y A h an n AlumGulch aw C o A H 2 y l a n u m rs a h !< T a C h G r w S e u o e 1 a R B lc n S C r h n s a a 82 a t n n a n e UV y ch r t !< B o a n C F r 9 a C 8 C r r n e u c e h r k z u h c !< n z 1 !< R 0 a R r i n M v i B e v ! a r r z o t e u S n C r v i !< a C a 289 R r C n UV S R r e i !< v u t e a e z k r Utilize WQ/Isotopes to refine MIKESHE flow calibration “The use of extreme events such as 100‐year floods, or droughts, or the input of management practices targeting erosion (vegetation, contouring, etc.) into these models would allow management to test outcomes and solutions to a wide variety of potentially damaging conditions with the goal of preventing costly loss or injury to lives or properties.” (Norman et al, 2008) Scenarios 1. Baseline Conditions (no mine dewatering) - 2014 to 2020 2. WTP2 discharge – 2014 to 2020 (7 years) 3. Dewatering Scenario (assumptions based on South32 presentation July 2020) Assumptions: − 4500 gpm discharged to Harshaw Cr from WTP2 − Continuous flow for 3.5 years, then off for 3.5 years − Includes hourly distributed weather and runoff Simulated Effects of WTP Discharge to Upper Harshaw Creek at Patagonia-Sonoita Cr. Preserve 4500 GPM WTP discharge Simulated Change in Flow Virtually all peak storm flows increase – significantly at Patagonia-Sonoita Cr. Preserve amplifying flood potential through town. Flows at TNC preserve increase 200 to 600%. Modeling shows discharge at preserve increases baseline surface flows MORE than WTP 4500 gpm (10 cfs). Precip from typical storm events runs off instead of infiltrating Nearly all of WTP discharge translates past Town. WTP Discharge Effects Area of Groundwater Rise extends nearly 3 miles around South32 Evaluation of WTP discharge Harshaw Creek - Unrealistic impacts on Harshaw and Sonoita Creek: • Shows no/minimal impacts on Sonoita Creek • Simulated Groundwater rise ~3 miles across Harshaw Cr: • MIKESHE shows impact along Harshaw Cr. limited to channel alluvium and bedrock just around creek (hundreds of feet – not 3 miles) • “Steady State” analysis doesn’t account for effects of subsurface saturation and storm events on streamflow. Estimated flow of 132 gpm Dewatering UV82 Bra nch 17 Bra Branch n 5 ch 19 Bran ch 2 Bran ch 18 MIKESHE Model Boundary B ranch 20 FortFort HuachucaHuachuca Bra nch 24 B r a n 4 c 1 h B 6 h ra c n n c ra h 3 B 2 2 2 h 83 nc Suggests dewatering to at least Bra Bra UV 12 nch ch 2 an 1 Br 82 2000’ elevation (>3000’ below 3 UV 1 6 ch 1 n h H a c ars r n h B a a r Santa Cruz w Branch 4 ground surface). B Cr Cochise eek AlumGulch B South32 Groundwater Model ra n 8 ch 9 h c So n an o r (purple line) only includes ita Cree k B South32_WTP_GroundwaterMOUND B ran ch South32_DrawdownExtent Harshaw Creek can’t assess 10 1 HermosaMine 1 h c MIKEHYDRO_HermosaMine_CrossSections impacts to Sonoita Cr upstream. an Br MIKEHYDRO_HermosaMine_Branches MSHEmodel_Sonoita UV289 19 §¨¦ Faults_MSHEcombinedREVISED Places (Outline) Model boundary clearly affects Cnty Bnds (detailed, named) MineGWmodelDOMAIN.JPG both drawdown (red line) and RGB Red: Band_1 groundwater mounding (green 19 ± Green: Band_2 §¨¦ £¤89 02.557.51.25 Blue: Band_3 line). UV189 Miles Simulated Water Level Drawdown • Assumed 600 m (1968 ft) dewatering depth. $ !( !( +$ Hard Luck 2 H !( a h AG 16-6 Ranch unnamed c 24-4 !( !( rsh n !( a • Specified drains in mine footprint. a w !( !( 4 +$ r C ch !( 20-5 r Bran B ee a !( k it k Canyon Creek o !( Red Roc k 3 n e MW-4 o e • Preliminary drawdown shows similar extent S r w C a 82 reek sh aC r onoit UV S a Soonnooiittaa Simulated Water Level HarshawDrawdownH (m) Indian Head to South32 (after 4 years), but is elongated Crreeeekk Creek Saddle Mountain Cott Tank unnamed Mountain Tank unnamed Alum Gulch unnamed +$ Iron Well +$") Harshaw Creek +$ Well Hars +$ along Alum Gulch (faulting). haw 2 AlumG") ulc h ") A l Middle Kennedy Flux Canyon u Meadow Spring m Harshaw2 +$ +$ Spring • Can’t compare to mine drawdown levels – +$ G Red Mtn H u ") a l Spring c rsh h k") +$ Red Mountain e aw ") re 1 C Lee's Well details unavailable. w +$ a h Turner Spring rs B a ra Unnamed H S n a Chinaman n ch 9+$") t • Predicted dewatering rate much lower Spring a 8 Flux Canyon C h +$") r ") Chinaman SW c Santa Cruz u Chinaman n z MOHAWK MINE a Unnamed r R CRACKER T e GRINGO Worlds Fair B JACK GRP m i WILLIE JOE $ v Mines MINE GROUP + p FRANCIS 1-4 BLUE JAY o e OAK RIDGE r Spring TNC updated flow status a STAR k r l Cree a 1 G anyon $ oni u B R C + FLOWatag STATUS l hree P c ra T h n c Perennial h BLUE LEAD IVANHOE MINE 3 S MINE GROUP 2 2 Sa Formerly Perennial ELLEN DELLA 2 h nt AND VANSUELLA c ta MAMMOTH MINE B Bra n C UNKNOWN ran B ru Regulated k CANDELERIO uz c r e h Br z 4 an a R re ch 21 R Aqueduct 2 iv C n iv a e h it r Effluent Dominated (May Be Formerly Perennial) c o UNKNOWN c n n a POWER'S h r o S PROSPECT Hydro routes B 1 Humbolt Upper Harshaw R 0 C M South32_DrawdownExtent CASTLE ed R Hale Ranch ea BUTTE MINE ock C o Creek Unnamed d anyon x Upper Harshaw ow Creek G ") F MIKEHYDRO_HermosaMine_CrossSectionsBLACK u Spring East ") la BUTTE lc t W SONOITA h Creek Unnnamed a 6 MIKEHYDRO_HermosaMine_BranchesGROUP s 1 PROSPECT TRES POBRES h SANSIMON MINE +$ ch HILLTOP Spring West+$ n Streams_all SANTA a r CRUZ MINE B TREASURE KING COPPER Cnty Bnds (detailed, named) SILVER EAGLE 1 AND 3 NEW YORK n B k e CHRISTMAS o r re a C GIFT MINE y n a FOUR METALS ch it n Hydro routes 6 no o ELAVATION HALE a 01230.5 S MINE GROUP PROSPECT #2 C Miles spring_data_HUC8a t +$ d l SULFIDE o PROSPECT springs_Schrag2020 b ") H AZTEC MINE SONOITA H GROUP CREEK-ALUM H m a ars a CANYON PLACERS VIRGINIA haw 3 u r 1 INVINCIBLE 1 AND 2 r s 1 South32_DrawdownExtent Alum PAT PROPERTY Hars s BLUE BIRD haw 2 H h Gu IRON CAP PROSPECT h lch 1,2,3 h c RED MOUNTAIN a n GARFIELD k a ra GROUP e ww B e HermosaMine r B C H CC !< r w a a a r n Santa Cruz sh rr c h a ee Farrell T h EXPOSED REEF s w Bedrock Drawdown (m) - 4 years h 9 BLUE EAGLE r e r a 1 e e MINE H kk Spring e WEST SIDE R HAMPSON ") C Upper Harshaw $ n e C n u Paja Verde -0.6 - 0 r v C a i JAVELINA 8 w r C S e WORLD'S a R 4 e CONLEY h h Spring w k OLD TIMER FAIR MINE c s ha KECK n r rs THREE R a a a 0.1 - 1 COPPER VOLCANO r H H MINE GROUP $ SEMCO MILL BROWN !< MONO B + NEW CHIEF DOMINO GOLD STANDARD HOPE MINE WELLINGTON JANUARY MINE GROUP 1.1 - 5 B GROUP GROUP AND NORTON M r e a !< a !< MINE GROUP do n w F c la BRADFORD MINE h COLLICELLO t W 5.1 - 25 AND LURAY n LIBRADA as 1 C o TRENCH MINE h 0 o MINE GROUPS y SUNNYSIDE x G n u a lc EUROPEAN C ALTA MINE h Basin Spring 25.1 - 612.3 VENTURA MINE GROUP t d SONDITA MINE GROUP l o HARDSHELL MINE b MINE +$ GROUP m AMERICAN MINE MIKEHYDRO_HermosaMine_CrossSections u H BLACK SALVADOR BOB LEE DENVER MINE EAGLE HARSHAW AND GROUP DISTRICT MIKEHYDRO_HermosaMine_Branches WIDOW MN-AG MANTO TRES DE MAYO BILLY "D" STANDARD COLOSSA MIN GROUP 11 PROSPECT h ESPERANZA BLACK ROSE nc THUNDER MINE Bra Guajalote Paymaster MSHEmodel_Sonoita AUGUSTA MINE BENDER Paymaster JARILLAMINE PROPERTY Peak GROUP Miller ") Faults_MSHEcombinedREVISED LA PALOMAR +$ +$ Spring ENDLESS CHAIN GOLDEN GATE Miller") Spring Harshaw 4 MORNING GLORY Places (Outline) O'MARA MINE MOLLIE GIBSON MOWRY ± +$ Nogales PROPERTY MOLYROCK Jackalo International MINNIE SMITH 01230.5 EL PASO Cnty Bnds (detailed, named) SORILLO Airport Mine Spring PHOENIX Miles BULLWACKER HOMESTAKE HAIST DEPOSITS +$ OLIVE UNKNOWN *# MAMMOTH MINE *# 3 ELLEN DELLA Branch 2 CANDELERIO *# Upper Mines Br AND VANSUELLA *#*# anch 2 Sonoita 1 South32_DrawdownExtentUNKNOWN Creek POWER'S PROSPECT HermosaMine *# Effect of Legacy CASTLE *# aa MIKEHYDRO_HermosaMine_CrossSections BUTTE MINE itaC ek itit no r e nnoo BLACK S o oo eekk MIKEHYDRO_HermosaMine_Branches *# SS ee H Branch B rr H 4 BUTTE CC a r SONOITA r Cnty BndsRedrock (detailed, named) GROUP a C rs Mines on n PROSPECT r h re ha TRES POBRES c e a Canyon # e w SANSIMON MINE MSHEmodel_Sonoita * HILLTOP h *# k # SANTA 2 * *# *# CRUZ MINE COPPER Temporal TREASURE KING Places (Outline) Proposed *#SILVER EAGLE 1 AND 3 Gulch Faults_MSHEcombinedREVISED CHRISTMAS*# *# *# B GIFT MINE HUC12 ran FOUR METALS ch ELAVATION*# # 6 JAVELINA z WORLD'S 8 z CONLEY u into Harshaw Creek Harshaw Creek u r *# h r OLD TIMER FAIR MINE r c r KECK C C e n e v a v a i COPPER # VOLCANO*# MONO r a i * t t B R R n SEMCO MILL # BROWN THREE R n * # # a # *# # * # WELLINGTON* a * * S # MINE GROUP CHIEF* S DOMINO* NEW HOPE *# *# GOLD STANDARD GROUP MINE GROUP*# MINE GROUP *# JANUARY COLLICELLO B AND NORTON BRADFORD MINE r AND LURAY “A significant component of a SUNNYSIDE MINE GROUP LIBRADA *# n c MINE GROUPS h 10 TRENCH MINE *# metal dispersion in these *# *# *# *# Lead Queen Mine VENTURA EUROPEAN SONDITA # ALTA MINE MINE GROUP MINE GROUP * watersheds is the circulation MINE *# HARDSHELL GROUP AMERICAN MINE *# MINE Discharge and eventual surface *# *# # BOB LEE DENVER MINE SALVADOR * AND *# HARSHAW # BLACK# discharge of waters that WIDOW * * DISTRICT TRES DE MAYO# *# STANDARD EAGLE MN-AG MANTO MIN GROUP * BILLY "D" PROSPECT GROUP 11 *# COLOSSA ch have absorbed metals and *# # THUNDER MINE *# ra n **# *# BLACK ROSE B ESPERANZA*# JARILLAMINE AUGUSTA MINE BENDER acidity via passage through GROUP *# Historical# Mines PROPERTY Proposed WTP * *# LA PALOMAR networks of underground GOLDEN GATE ENDLESS CHAIN*#*#MORNING GLORY *# mine tunnels.” Impacting Water O'MARA MINE discharge location *# MOLYROCK MINNIE SMITH *# MOLLIE GIBSON Nogales # *# (Norman et al, 2008) International Quality in Harshaw * *# EL PASO MOWRY PROPERTY Airport *# HOMESTAKE # PHOENIX HAIST * *# OLIVE BULLWACKER *# *# DEPOSITS 01230.5 *# OFF POINTER Miles MAY PAYMASTER *# *# *# # PATAGONIA PLACERS * ROY*# CONCLUSIONS AND RECOMMENDATIONS Key Findings from MIKESHE Modeling • Important details influencing flows: − transient shallow groundwater, shallow bedrock, clay in soil zone • MIKESHE results differ from APP show a range of impacts through Town. • Impacts derive from entire watershed upstream of Lake Patagonia • A fully integrated modeling tool is needed to simulate: − the dynamically coupled GW‐SW flow conditions − continuous response to each storm event − flows in ungauged watersheds WTP2 DISCHARGE Conclusions Proposed WTP2 discharge is likely to: 1. Quickly saturate/fill shallow alluvial aquifer along Harshaw Creek 2. Flow through Town and Preserve after initial wetting period 3. Increase PEAK flows downstream on Harshaw and Sonoita Cr. through Town and Preserve by more than WTP2 discharge 4. Facilitate transport of any contaminants above the WTP2 to downstream areas 5. Raise groundwater levels along both Harshaw and Sonoita creeks MINE DEWATERING Conclusions Findings from dewatering simulation in MIKESHE: − Lateral extent similar to South32’s July 2020 presentation (though uncalibrated) − Dewatering rate much lower than South32 details of dewatering/local geology at mine unavailable − Numerous springs within drawdown footprint − Faults likely influence drawdown and infiltration and could translate drawdown to Sonoita Creek • Remaining Questions: 1. Will mine dewatering & treatment address WQ at intercepted legacy mines inside and outside mine footprint? 2. How will post‐mining water level recovery and discontinuation of WTP discharge affect baseline conditions along Harshaw and Sonoita creeks? 3. What will be long‐term post‐mining WQ impacts? Missing in South32 analysis of WTP2 impacts Item Description Variable bedrock depths Variable-depth low-permeability bedrock important constraint on potential stream infiltration and saturation. Must develop geologic model based on boreholes and/or geophysical survey. Lithologic variations above bedrock – Review of numerous logs most wells show notable clay layers, which reduce stream substantial clay layers infiltration/storage potential. Need more complete geologic model based on logs. Variable/dynamic GW table – Available water level data show relatively shallow water table limits stream beneath Harshaw and Sonoita infiltration/aquifer storage potential. A broader model needs to be prepared to simulate groundwater flow/stream interaction. Creeks Sonoita Creek inflows above Lack of gage data at this location requires calibrated modeling of continuous, long-term Harshaw Creek coupled groundwater-surface water flow conditions – entire catchment upstream of confluence. Distribution and dynamics of soil Not accounted for; should use available detailed soil survey data. Must consider transient moisture effects (antecedent conditions). Storm runoff inflows along Harshaw AZDEQ identified water quality issues with legacy mines upstream of WTP discharge point. upstream of WTP2 discharge point Storm runoff above WTP2 may transport contaminants and add flow to area downstream of WTP2. Must model entire catchment above WTP2. DATA GAPS 1) High‐resolution topography (LiDAR) of Harshaw‐Sonoita Creek system 2) More detailed characterization of alluvial aquifer along Harshaw Cr 3) Mapped legacy mine footprints/adits/tunnels/shafts, etc. 4) Details of mine water use throughout 30‐year mine life 5) Geologic model based on well logs/geophysics 6) Continuous groundwater‐level monitoring in wells along Harshaw and Sonoita creeks and in upland recharge areas 7) Continuous stream‐flow measurements (every 5 minutes) a. upstream and downstream of WTP2 discharge point on Harshaw Cr. b. Sonoita Cr. upstream and downstream of Town 8) Wet/dry mapping of key ephemeral/intermittent stream reaches above and below Town 9) High‐resolution meteorological data 10) Pumping/diversion data 11) More frequent/informed WQ monitoring at WTP2 and POCs –capture notable runoff events in Harshaw Cr 12) Hydraulic testing ‐ aquifer testing, long term dewatering pumping Modeling Recommendations • Conduct a more rigorous analysis − Use “integrated’ code like MIKESHE (vs single-process codes like HEC or MODFLOW) to capture highly dynamic groundwater-surface water interactions − Model full hydrologic system upstream/upgradient of Patagonia Lake • Collect additional data (data gaps list) for at least 1 year • Develop 3D geologic model for entire watershed – including bedrock depth, faulting and alluvial lithology • Improve calibration to available data (~last 20 years) to reproduce: • complete storm hydrographs, especially large events • average and transient well water levels (and springs) • actual evapotranspiration − Develop local-scale (eg, 40-m) model of Harshaw/Sonoita Cr through Town to examine: • Dewatering with WTP discharge • Mining alternatives − Conduct formal uncertainty analysis • Assess range of impacts • Identify worst case • Peer review work APPLICATIONS OF INTEGRATED MODEL 1. Assessments: Erosion impacts from additional flows from WTP2 Spring hydrology ET changes (increased flows, wetted area, vegetation) Long‐term water quality changes Climate Change 2. Mitigations (examples): Possible reservoir on tributary upstream of town to store WTP discharge, thereby: . Minimizing flooding in Harshaw/Sonoita creeks . Providing controlled supply of water to town . Enhancing wetland habitat Passive wetland treatment system to mitigate long‐term water quality impacts to Harshaw & Sonoita creeks and enhance habitat Erosion‐control structures (single‐rock dams, gabions, road swales, etc.) Thank you! Laurel Lacher Lacher Hydrological Consulting [email protected] Bob Prucha Integrated Hydro Systems [email protected] B ranc Upper Pig Camp $h 21 2 +$ + h Spring Copper c Sonoita Box Canyon B n Mountain r a a r Creek unnamed n Smith Spring unnamed c +$B h +$+$ ttaa 6 ii Cottonwood nnoo Redrock Temporal oo eekk Falls Spring Effects of SS ree $ Ranch Spring r + Gulch CC Branch4 +$ H unnamed a Sonoita C rs C sh rre ha Sewage Pond ee aw ek w Sansimon Dewatering and unnamed k Mine unnamed +$ $ Gate Spring + +$ Redrock D-22-15 Hard Luck H 15ACB Ranch unnamed ar Canyon WTP discharge on sh a Spring w +$ C +$ reek Branch 4 Springs, during UV82 reek noitaC o Harshaw S Indian Head Creek Saddle Mountain Mountain and post-mining unnamed Tank unnamed Cott Tank Alum Gulch unnamed $ +$ Iron Well Well +$") Harshaw Creek +$ + h ")AlumGulc ") Kennedy Spring Flux Canyon Meadow Spring +$ Red Mtn +$ +$ Lee's Well Spring ") Middle ") +$") Red Mountain Middle Turner Spring Sonoita Harshaw2 +$ Creek Unnamed Chinaman Bra ") nc+$ Flux Canyon h Spring 9 ")+$") Chinaman 8 Harshaw Creek h Unnamed Chinaman SW Worlds Fair c n +$ Spring ra +$ B South32_DrawdownExtent HermosaMine Humbolt Upper Harshaw Upper Harshaw Creek Unnamed Hale Ranch MIKEHYDRO_HermosaMine_CrossSections ") Creek Unnnamed B Spring East ") Santa Cruz MIKEHYDRO_HermosaMine_Branches ran Spring West ch +$ 10 +$ Cnty Bnds (detailed, named) ") springs_Schrag2020 +$ spring_data_HUC8a S MSHEmodel_Sonoita S a a n n t t 1 a h 1 Places (Outline) a C nc C a r r r B u Faults_MSHEcombinedREVISED u z z Farrell R R HUC12 i i Upper Harshaw v Spring v e e r ") +$") 01230.5 Guajalote Paymaster Upper Sonoita Creek MilesPeak Paymaster ")$ Spring +$ ") Miller +