Engineering analytics presented information on the groundwater modeling performed for the Rosemont Copper Project to a group of well owners. The presentation was given on April 3, 2012.

1. Rosemont Groundwater
Presented to
Well Protection Program
Informational Meeting
April 3, 2012

2. Presenter
n Grady O’Brien, Engineering Analytics, Inc.
n Professional Geologist / Hydrogeologist
n U.S. Geological Survey – 14 years
n Denver and Tucson
n Groundwater Consulting – 9 years
n Rosemont groundwater modeling project lead for
Tetra Tech
n University of Wyoming / Colorado School of Mines
n Project focus in desert southwest – AZ, NV, UT
April 3, 2012 2

3. Discussion Outline
n Rosemont Project Groundwater Related Highlights
n Supporting Scientific Studies and Data
n Understanding the Groundwater Flow System
n Bedrock / Fractures / Geologic Structures
n How the Open Pit Effects the Groundwater System
n Will my well go dry?
April 3, 2012 3

4. ROSEMONT SITE LOCATION
4
April 3, 2012

5. WELL PROTECTION AREAS
April 3, 2012 5

6. ROSEMONT PROJECT
Hydrologic Highlights
n Open pit mine
n 2,000+ feet deep
n ~ 1 mile in diameter
n Pit dewatering for 22 year life of mine
n Open pit is major feature that will impact
groundwater levels
n Terminal Pit-lake predicted after mining
April 3, 2012 6

7. SCIENTIFIC STUDIES
Supporting Groundwater Flow Modeling
3-D hydrogeologic model
n Extensive data
available
n Many data types
n Coverage across
region
n Best available data
used
April 3, 2012 7

8. SCIENTIFIC STUDIES
Supporting Groundwater Flow Modeling
n Geology Wells used for model calibration
n Site and regional scales
n 3-dimensional model
n Wells
n 730+ water-levels for
model calibration
n Lithology / geology
n Water quality
n Aquifer Tests
April 3, 2012 8

9. SCIENTIFIC STUDIES
Supporting Groundwater Flow Modeling
Springs and riparian vegetation
n Springs and Streams
n Discharge measurements
n Water-quality data
n Isotope data
n Riparian vegetation
n Distribution
n Type
April 3, 2012 9

10. SCIENTIFIC STUDIES
Montgomery & Associates
n Geology / Hydrogeologic Units
n Aquifer tests / Hydraulic properties
n Short-term and Long-term tests
n Regional data
n Riparian vegetation evapotranspiration (ET)
n Water levels and water quality
n Spring flows and water quality
n Groundwater flow models
April 3, 2012 10

11. SCIENTIFIC STUDIES
Tetra Tech
n Site Water Management
n Infiltration analysis
n Infiltration, seepage, fate, and transport
modeling
n Storm-water runoff
n Davidson Canyon conceptual model
n 3-dimensional hydrogeologic model
n Groundwater flow model
April 3, 2012 11

12. SCIENTIFIC STUDIES
Other Contributing Sources
n Arizona Geological Survey
n Geologic mapping
n Pima Association of Governments
n Cienega Creek and Davidson Canyon
n Groundwater flow model
n U.S. Geological Survey
n Stream flows
n San Pedro and Tucson basin flow models
n Several recharge analyses
April 3, 2012 12

13. GROUNDWATER FLOW MODELS
n Two regional groundwater
flow models
n Simulate different geologic
conditions to provide wider
range of impacts
n Davidson Canyon Fault Zone
n Davidson Canyon Dike
n Backbone Fault / Flat Fault
n Extensive third-party peer
review approved models
April 3, 2012 13

14. GROUNDWATER FLOW SYSTEM
n Fractured bedrock
n Alluvium – limited layer on top of bedrock
n Major geologic structures
n Faults (Backbone, Flat, Davidson Canyon)
n Davidson Canyon dike
n High water levels near the proposed open pit
n Groundwater flow paths
n From pit area flow is predominately down Davidson Canyon
n From upper Cienega Creek basin, flow is into lower Cienega
Creek
April 3, 2012 14

15. Current
Water
Levels
and
Flow Direction
Shading illustrates large
hydraulic gradient area
indicating limited
groundwater flow and weak
fracture connections
April 3, 2012 15

16. FRACTURED BEDROCK
n Very low bedrock permeability
n Low water storage in fractures
n Groundwater flows in fractures
n Connections between fractures
n How far do fracture connections extend?
n Aquifer testing and water levels indicate that
pit area is not well connected to other areas
April 3, 2012 16

17. FRACTURE CONNECTIONS
Influence of Persistence of Discontinuity on the Degree of
Fracturing and Interconnectivity
High water levels in pit area indicate that fractures are not well
connected to lower elevation areas. Water would drain rapidly
from pit area if strong connection existed.
April 3, 2012 Anderson, M.P. and Woessner, W.W., 2002, Applied Groundwater 17
Modeling: Academic Press, San Diego, CA, 381p.

18. WELLS MUST INTERSECT
FRACTURES TO PRODUCE WATER
This is why neighbors may have different results with nearby wells.
18
If water April 3, 2012
producing fractures were common, everyone would have high producing wells.

19. FRACTURE CONNECTIONS BETWEEN
the PIT and YOUR WELL
n “What if there is a fracture between the pit
and…”
n Evidence supports lack of fracture connection
n High water-levels in pit area – water not flowing
‘downhill’ because fractures are limited
n Varying productivity with on-site wells show
limited fracture connectivity across the site
n No high discharge perennial springs in area
n Conclusion is weak fracture connection
April 3, 2012 19

20. FRACTURE CONNECTIONS BETWEEN
the PIT and YOUR WELL
n “The pit will suck in all of the groundwater…”
n In the long term, consumptive use of the pit
lake is predicted to be 100 to 230 gpm
n Equivalent to a few water-supply wells
n This water is “captured” from across the region
n Evaporation on the pit-lake surface is
“consuming” groundwater, but it is limited
n Not physically possible to remove all of the
groundwater
April 3, 2012 20

21. WILL MY WELL GO DRY?
n Water levels will decrease
dramatically in the immediate pit area
n Water-level drawdown diminishes
rapidly away from pit area
n Which wells will go dry depends on
site specific hydrogeologic conditions,
well location, and well depth
Geologic map illustrating complex
April 3, 2012 geology that influences drawdown
21
propagation

22. DEWATERED PIT
n Conceptual
cross
section
through the
pit (with
vertical
exaggeration)
April 3, 2012 22

23. TERMINAL PIT LAKE
HYDRAULIC SINK
n Conceptual
cross
section of
the pit lake
after
mining
ends (with
vertical
exaggeration)
April 3, 2012 23

24. PREDICTED WATER LEVELS
n Montgomery and
Associates flow
model
Water levels and flow
directions 1,000 years after
mining ends.
Flow directions similar to
pre-mining with exception of
pit-lake capture zone
With cross section location
lines used on following slides
April 3, 2012 24

25. PREDICTED WATER LEVELS
Section X-X’
Drawdown decreases rapidly away from pit
Water flow flows water table, not land-surface elevation
April 3, 2012 25

26. PREDICTED WATER LEVELS
Section Y-Y’
Drawdown decreases rapidly away from pit
April 3, 2012 26
Water flow flows water table, not land-surface elevation

27. PREDICTED WATER LEVELS
Section Z-Z’
Drawdown decreases rapidly away from pit
April 3, 2012 27
Water flow flows water table, not land-surface elevation

28. WELL PROTECTION AREAS
Explanation
Detailed Map Area
! Well Location
Extent of Ultimate Pit
Davidson Canyon Dike
Proposed Tailings and
Waste Rock Facilities
Davidson Canyon
Watershed Boundary
Surface Hydrogeology
Qal Quaternary and Recent Alluvium
QTg Late Tertiary Alluvium
QTg1 QTg1
QTg2 QTg2
Tsp Tsp
Tgr Late Cretaceous/Tertiary Intrusives
Kv Upper Cretaceous Volcanics
Ksd Lower Cretaceous Bisbee Group
Pz Cambrian and Paleozoic Formations
PCc PreCambrian Granodiorite and Schist
0 1 2 3
April 3, 2012 Miles 28

29. HILTON RANCH AREA
Explanation
Wells
! Groundwater Site Inventory
! 55 Wells
! Model Targets
Davidson Canyon Dike
Davidson Canyon
Watershed Boundary
Davidson Canyon Dike
may limit drawdown in
this area
April 3, 2012 29
0 1,500 3,000 4,500
Feet

30. SINGING VALLEY NORTH AREA
Explanation
Wells
! Groundwater Site Inventory
! 55 Wells
! Model Targets
Extent of Ultimate Pit
Davidson Canyon
Watershed Boundary
Proposed Tailings and
Waste Rock Facilities
Surface Hydrogeology
Qal Quaternary and Recent Alluvium
QTg Late Tertiary Alluvium
QTg1 QTg1
QTg2 QTg2
Tsp Tsp
Kv Upper Cretaceous Volcanics
Ksd Lower Cretaceous Bisbee Group
PCc PreCambrian Granodiorite and Schist
0 1,500 3,000 4,500
April 3, 2012 30
Feet

31. HELVETIA AREA
Explanation
Wells
! Groundwater Site Inventory
! 55 Wells
! Model Targets
Extent of Ultimate Pit
Davidson Canyon
Watershed Boundary
Proposed Tailings and
Waste Rock Facilities
Surface Hydrogeology
Qal Quaternary and Recent Alluvium
QTg Late Tertiary Alluvium
QTg2 QTg2
Tgr Late Cretaceous/Tertiary Intrusives
Ksd Lower Cretaceous Bisbee Group
Pz Cambrian and Paleozoic Formations
PCc PreCambrian Granodiorite and Schist
April 3, 2012 0 1,500 3,000 4,500
31
Feet

32. PREDICTED GROUNDWATER
LEVEL DRAWDOWN
Drawdown contours are composite, worst
case from M&A and Tetra Tech flow models
Areas within 10-foot drawdown prediction
after 150 years are included in Well
Protection Program
April 3, 2012 32

33. GROUNDWATER LEVEL
FLUCTUATIONS
Large water-level fluctuations can occur with no mining effects
Short Term Long Term
Time Period 3 years
37 to 55 years
(2007-2009)
No. of Wells 14 52
Minimum Fluctuation (ft)
0.7 0.7
Maximum Fluctuation (ft)
33.1 69.0
Average Fluctuation (ft)
7.1 19.7
(Montgomery & Associates, 2010b)
April 3, 2012 33

34. MONITORING WELLS
n Determine long-term trends and mine-induced
impacts
n Early warning for mitigation
n On-going monitoring network
n Wells and springs
n Point of Compliance wells
n Required in ADEQ Aquifer Protection Permit
n Davidson Canyon wells (proposed)
n Sentinel Wells (planned)
April 3, 2012 34

35. MONITORING WELLS
n Proposed
Davidson
Canyon
monitoring
wells
n Near Hilton
Ranch area
April 3, 2012 35

36. MONITORING WELLS
n Homeowner wells
n Rosemont is seeking volunteer homeowners
n Document water levels so that mining impacts
can be determined
n Start prior to mining
n Simplify potential future claim process
n Minimal disturbance to homeowner
April 3, 2012 36

37. CONCLUSIONS
n Different groundwater models result in similar predictions
n Provides confidence that predictions are reasonable
n Rate and direction of drawdown propagation will vary
n Different areas will have different impacts
n Away from the immediate pit area predicted drawdown is
within the range of natural fluctuations
n Beneficial for homeowner’s to obtain history of water-
level changes by volunteering to allow measurements
in their wells
April 3, 2012 37