Tucson Office 3031 West Ina Road

Tucson, AZ 85741 Tel 520.297.7723 Fax 520.297.7724

www.tetratech.com

Technical Memorandum Barrel Only Alternative

Noise Analysis

To: Kathy Arnold From: Robert Sculley

Company: Rosemont Copper Company Date: January 15, 2010

CC: Jamie Sturgess (Rosemont); David Krizek; Michael Dieckhaus (Tt)

Doc #: 025/10-320871-5.3

1.0 Introduction This Technical Memorandum was prepared by Tetra Tech and presents a Noise Analysis for the Barrel Only Alternative being considered in the US Forest Service Environmental Impact Statement (EIS) for the proposed Rosemont Copper Project (Project). This analysis assesses the potential impacts that the Barrel Only Alternative will have on noise conditions.

Tetra Tech published a comprehensive Supplemental Noise Study Report in April of 2009 that was based on the facility layouts in the Mine Plan of Operations (MPO). The Noise Study provided data on existing noise levels in the vicinity of the Project and noise levels measured at an active copper mine such as blasting and other operational activities. Modeling of the blasting vibrations was also performed. Noise effect contouring in the April 2009 study was based on the MPO facility layouts.

The following provides a comparison between the MPO and the Barrel Only Alternative facility layouts:

The top surface of the Dry Stack Tailings Facility would be about 5,250 feet above mean sea level (amsl) for the MPO, and about 5,300 feet amsl for the Barrel Only Alternative. The Dry Stack Tailings Facility for Barrel Only Alternative would have a footprint of 987 acres compared to 870 acres under the MPO.

The top surface of the Waste Rock Storage Area would be about 5,450 feet amsl for the MPO. The Barrel Only Alternative would have two (2) sections to the Waste Rock Storage Facility, with the larger south section having a top elevation of 5,700 feet amsl and the smaller east section having a top elevation of 5,200 feet amsl. The footprint of the Waste Rock Storage Area would be 1,460 acres under the Barrel Only Alternative, compared to 2,000 acres for the MPO.

The Heap Leach Pad for the MPO would be constructed in two (2) phases. The leach pad for the Barrel Only Alternative would be constructed in one (1) phase with

2

a smaller total footprint. In both cases, the closed heaps would eventually be covered with waste rock.

Under the Barrel Only Alternative, the combined footprints of the Waste Rock Storage Area and Dry Stack Tailings Facility (about 2,450 acres) would be somewhat smaller than the combined footprints under the MPO (about 2,870 acres). Under the Barrel Only Alternative, the Dry Stack Tailings Facility would not extend as far to the northeast as it would under the MPO and the Waste Rock Storage Area would extend further to the east than it would under the MPO.

The location and size of the Open Pit would be the same under both the MPO and the Barrel Only Alternative.

Under the Barrel Only Alternative, the Plant Site facilities would have a slightly different configuration and footprint than under the MPO. Under the Barrel Only Alternative, the Waste Rock Storage Area and the Dry Stack Tailings Facility would shield the Plant Site from State Route 83 (SR 83) only for SR 83 segments a mile or more south of the Primary Access Road.

The Primary Access Road would be in the same location under both the MPO and the Barrel Only Alternative.

The differences between the Barrel Only Alternative and the MPO are mostly matters of small details, not major features that would affect noise impacts. Consequently, most of the noise and vibration impact discussions, and the associated noise contour figures in the April 2009 Noise Study, are applicable to the Barrel Only Alternative. Differences in the shape of the combined Waste Rock Storage Area and Dry Stack Tailings Facility would, however, result in some changes in the potential locations for operation equipment under the Barrel Only Alternative.

The following sections of this Technical Memorandum explain which results of the April 2009 Noise Study are still applicable to the Barrel Only Alternative and which results would change under this alternative.

2.0 Blast Noise and Blast Vibration Impacts The Open Pit would be in the same location and operated in the same manner under both the MPO and the Barrel Only Alternative. Blasting events would be limited to one (1) event per day. Daily explosives usage is also expected to be the same under both scenarios.

In addition, differences in the maximum height and shape of the combined footprints of the Waste Rock Storage Area and the Dry Stack Tailings Facility would produce only minor localized shielding differences for blast noise under the MPO and the Barrel Only Alternative. Blast noise effects at the closest noise-sensitive receptor locations would not be affected by differences in the combined footprints of the Waste Rock Storage Area and the Dry Stack Tailings Facility under the MPO and the Barrel Only Alternative.

Because blasting events would be similar under both the MPO and the Barrel Only Alternative, groundborne vibrations would be the same. Thus, the discussions and associated noise contour

3

figures for blast noise and blast-related vibrations, as presented in the April 2009 Noise Study, would be applicable to the Barrel Only Alternative.

3.0 Construction Noise Impacts Although the Plant Site would still be in the same general area under the Barrel Only Alternative, the Plant Site facilities would have a slightly different configuration and footprint than that of the MPO. However, there would be little if any difference in the construction activity noise levels between the MPO and the Barrel Only Alternative. As noted in the April 2009 Noise Study, construction noise levels would attenuate to background noise levels over a relatively short distance and would not create any noise impacts at the nearest existing residences. Therefore, the discussions and associated noise contour figure for construction noise impacts presented in the April 2009 Noise Study would be applicable to the Barrel Only Alternative.

4.0 Equipment Operation Noise Impacts As discussed in the April 2009 Noise Study, operational noise levels from the Plant Site area would be similar to the maximum construction noise levels. Operational noise levels are expected to attenuate to background noise levels over a distance of about two (2) miles and would therefore not create any noise impacts at the nearest existing residences or along SR 83.

As indicated in Section 1.0, the combined footprints of the Waste Rock Storage Area and Dry Stack Tailings Facility under the Barrel Only Alternative (about 2,450 acres) would be somewhat smaller than the combined footprints under the MPO (about 2,870 acres). Maximum elevations of these facilities would be somewhat higher under the Barrel Only Alternative than under the MPO. Under the Barrel Only Alternative, the Dry Stack Tailings Facility would not extend as far to the northeast as it would under the MPO and the Waste Rock Storage Area would extend further to the east than it would under the MPO.

Figure 1 presents operational equipment noise contours for the Barrel Only Alternative. Actual noise generation by equipment working on the Waste Rock Storage Area and the Dry Stack Tailings Facility would be the same as for the MPO, but potential equipment locations would be somewhat different due to differences in the shapes of facility footprints.

Haul trucks and other equipment working at the south end of the Waste Rock Storage Area would be in a location very similar to that under the MPO. Consequently, the equipment operation noise contours shown in the April 2009 Noise Study for the south end of the Waste Rock Storage Area would still be applicable to the Barrel Only Alternative for equipment operations in the southernmost portion of the Waste Rock Storage Area. The eastern extension of the Waste Rock Storage Area under the Barrel Only Alternative would result in haul truck and other equipment operations being about 0.3 miles closer to homes along Singing Valley Road than would be the case under the MPO. Figure 1 shows the noise contours for equipment operating at the southeastern corner of the Waste Rock Storage Area. Intermittent equipment operations at the southeastern corner of the Waste Rock Storage Area would increase noise levels at the closest residences along Singing Valley Road by about 2 dBA compared to MPO operations at the south end of the Waste Rock Storage Area (from about 39 dBA to about 41

4

dBA). Most people cannot distinguish a change in noise level that is less than about 1.5 to 2 dBA. In addition, as noted in the April 2009 Noise Study, existing minimum noise levels in the Project area are estimated to be about 30 to 40 dBA, and average noise levels were generally 37 to 45 dBA. Because intermittent equipment operation noise levels would be comparable to existing background noise levels, the change to the Waste Rock Storage Area footprint for the Barrel Only Alternative would not result in a significant noise impact at the nearest noise-sensitive locations.

Equipment working at the north end of the Dry Stack Tailings Facility would be further from homes located along Highway 83 northeast of the Project site than would be the case under the MPO. Figure 1 shows noise contours for equipment operating at the north end of the Dry Stack Tailings Facility. Noise from such equipment operations would not result in any significant noise impacts at the nearest noise-sensitive locations.

5.0 Traffic Noise Impacts The Barrel Only Alternative would not alter the basic employment level or operating material requirements for the Project as described in the MPO. In addition, this alternative would not alter the routing of the proposed Primary Access Road. Consequently, the MPO and the Barrel Only Alternative would be expected to have the same traffic generation, and thus the same resulting traffic noise impacts. Therefore, the discussions and noise contour figures, as presented in the April 2009 Noise Study, would be applicable to this alternative.

6.0 Conclusion A review of operational and facility changes was performed between the MPO and the Barrel Only Alternative being considered in the EIS process. Because the facilities, operations, and anticipated traffic patterns are generally the same for both scenarios, most of the discussions, noise contour figures, and analysis results presented in the April 2009 Noise Study are applicable to the Barrel Only Alternative. Revised noise contours (Figure 1) were prepared to illustrate maximum equipment operation noise conditions under the Barrel Only Alternative. Compared to the MPO, maximum equipment operation noise levels under the Barrel Only Alternative would increase by about 2 dBA at the closest noise sensitive receptor location. Intermittent equipment operation noise levels under this alternative would be comparable to existing background noise levels, and would not cause significant noise impacts at the nearest noise-sensitive receptors.

5

REFERENCES Tetra Tech (2009) Supplemental Noise Study, Rosemont Copper Project. Prepared for

Rosemont Copper Company. Report Dated April, 2009 WestLand (2007) Rosemont Project Mine Plan of Operations. Prepared for Rosemont Copper

Company. Report Dated June, 2007

FIGURE

!(

!(

l

l

×

×

×

× ×

×

×

×× ××××

×

×××× ×

×

×

×

×

î

T 18 S

T 18 ST 19 S

T 17 S

T 18 S

T 18 ST 19 S

R 1

6

R 1

5

R 1

6 E

R 1

7 E

R 1

6 E

R 1

5 E

R 1

6 E

R 1

7 E

!(83

!(83

40 d

BA

50 d

BA

30 d

BA

80 dBA

70 dBA

60 dBA

40 d

BA

50 d

BA

30 d

BA

SINGING VALLEY RD

E GREATERVILLE RD

OLD

SO

NO

ITA

HW

Y

BIG

THU

ND

ER R

D

BIG THUNDER RD

GHOST DANCE RD MES

QU

ITE M

ESA P

L

35 dB

A

55 dBA45 dBA

55 dBA

45 dBA

35 dBA

80 dBA

70 dBA

60 dBA

SON

OITA H

Y

S HELVETIA RD

GR

EAT

ERVI

LLE

RD

E FISH CANYON RD

E EMPIRE RANCH RD

BOX C

ANYO

N R

D

S H

OU

GH

TON

RD

E YUCCA ASH FARM RD

E SINGING HILLS TR

S O

LD S

ON

OIT

A H

Y

HILTON RANCH RD

E BEATTY RANCH RD

W CAMINO AURELIA

YON EDG

E TR

E GARDNER CANYON RD

HIDDEN VALLEY RD

T 17 S

House Y

House X

House W

House V

House UHouse T

House S

House R

House Q

House P

House OHouse N

House L

House K

House JHouse I

House H

House D

House C

House B

House A

House E

Building F

Building G

Center of Open Pit

Plant SiteLocation

Santa Rita Abbey

North End of Dry Stack Tailings Facility

Southeast Corner of Waste Rock Storage Area

!(

!(

!(

!(

l

l

×

×

×

× ×

×

×

×× ××××

×

×××× ×

×

×

×

×

î

4100

4500

4400

4200

4700

4300

4000

4600

4800

4900

5000

5100

39003800

5200

5300

5400

5500

5600

3700

3600

5700

5800

3500

5900

6000

3400

6100

6300

6200

4300

4800

6000

5800

4600

4800

5300

4300

4100

5500

4900

4800

4700

5000

5100

5100

5500

5100

6200

4400

5100

520056

00

5400

5300

4500

6000

5000

6100

4500

4900

4900

5200

4200

4600

5600

4900

4900

4300

4000

4500

4000

4700

5300

4300

4800

4400

5900

5900

4900

5000

5100

4600

5100

4400

4600

4500

4100

4500

5400

4600

4200

4600

4600

4600

5000

5500

61006200

5100

5200

5200

4400

4400

5900

5900

4200

4400

4900

50004900

46004000

5300

4600

5400

6100

4800

4700

4000

4600

5300

4400

5300

4300

5000

4200

5500

4600

4600

5200

4500

4000

5400

5600

5300

5300

5000

5800

4200

5100

4600

4900

4700

4000

4700

5200

5400

5500

4600

4700

4600

5700

5300

5500

4300

5200

5400

4900

4200

5800

4100

5000

5700

6000

4700

5900

4600

4200

6100

5800

4400

5900

4000

4800

5300

4300

5200

5200

4800

5900

5200

4300

5000

5700

4800

5300

6200

4600

4400

5000

4300

5600

4100

5500

4700

4400

4700

50006000

4800

6000

5000

4700

5500

4800

4500

4500

5300

5100

4000

4700

4600 4000

4300

4500

5400

5200

4700

6000

4600

4800

4500

4300

4000

4200

5800

4200

4300

5900

4200

5400

4500

5400

5400

5700

4700

4600

4900

5700

4600

4500

5100

5800

4900

4700

4700

5000

4600

6000

4400

5100

4200

4600

4400

4600

5900

5000

5500

4600

5300

5400

5400

5300

4600

4900

4500

4300

4500

4500

4500

5300

4600

4100

5600

4900

4600 4700

4900

4100

5400

5700

4800

5200

4100

4900

4400

4600

4500

5000

4300

5400

5300

5400

5100

5600

4800

4500

4600

5900

5000

5300

4600

4200

4000

6200

5500

4000

4600

4500

4200

4600

4000

4300

5000

5000

5200

5300

4700

4000

4800

5000

5300

5000

4800

4100

4600

5200

5800

5000

5900

5800

5800

5000

4900

5700 4600

5400

5000

4400

4900

4900

4600

4600

5500

4200

5000

5300

4400

5400

4600

5400

4300

4300

5100

4500

4100

4800

5700

5100

6100

4800

5100

4700

4100

4200

5700

5500

4600

5400

4500

4700

4900

5300

4700

4800

5300

5700

11

11 11

11

07

01

14 18

17

12

30

04

26

16

29

08

27

32

14

19

35

28

25

26

15

10

09

21

33 3432

22

27

27

31

29

14

05

23

35

20

26

10

33

2223

12

23

15

26

13

20

03

28

13

09

24

29

28

29

20

31

16

31

0602 02

30

14

24

29

35

26 25

21

08

32

2024

1713 18

30

17

34

12

31

07

32

30

25

23

19

18

19

17

36

30

08

02

35

01

07

0503

29

18

26

06

0606

25

04

19

36

0102 05

07

08

30

05

13

36

01

24

25

36

25

12

36 3635

32

31

3532 343331

20

19

2221

2323

2024 19 24

09

16

04

21

33

28

28

33

09

04

16

21

27

34

28

34

27

15

22

10

22

27

15

03

03

10

3334

2122

±

JANUARY 2010

FIGURE 1BARREL ONLY ALTERNATIVE

ROSEMONT COPPER PROJECT NOISE ANALYSIS

4,000 0 4,000 8,0002,000Feet

Note: Equipment operationnoise contours are shown forthe north end of the Dry StackTailings Facility and thesoutheast corner of the WasteRock Storage Area, andrepresent intermittent noiselevels when equipment isoperating in these areas.Traffic noise contours are 24-hour Ldn noise levels for Year20 traffic conditions.

LegendMain Facility Outline

RoadwayAZ State Highway 83

Township/Range Line

Section Lines

Ground Contour

55+ dBA Ldn Zone

45-55 dBA Ldn Zone

35-45 dBA Ldn Zone

Equipment Noise Contour (XX dBA)

Traffic Noise Contour Designations

Transmittal of Technical Memoranda and Pit Lake Report

February 8, 2010

To: Beverly Everson

Cc: Tom Furgason

From: Kathy

Doc #: 003/

Subject:

Date:

OSEMONT COPPER A Bridge to a Sustainable Future.

Memorandum

Rosemont Copper is pleased to transmit the following twenty technical memoranda and one report:

1. Rosemont Hydrology Method Justification, a Tetra Tech memo dated January 7, 2010; 2. Barrel Only alternative —

a. Noise Analysis, a Tetra Tech memo dated January 15, 2010 b. Traffic Analysis, a Tetra Tech memo dated January 8, 2010

c. Geochemical Characterization 'of Facilities, a Tetra Tech memo dated January 10, 2010 d. Lighting, an M3 memo dated December 2009

3. Barrel and McCleary alternative —

a. Noise Analysis, a Tetra Tech memo dated January 9, 2010 b. Traffic Analysis, a Tetra Tech memo dated December 15, 2009

c. Geochemical Characterization of Facilities, a Tetra Tech memo dated December 16, 2009

d. Lighting, an M3 memo dated December 2009

4. Scholefield Tailings and McCleary Waste alternative —

a. Noise Analysis, a Tetra Tech memo dated January 15, 2010

b. Traffic Analysis, a Tetra Tech memo dated January 12, 2010

c. Geochemical Characterization of Facilities, a Tetra Tech memo dated January 10, 2010

d. Lighting, an M3 memo dated January 2010

5. Sycamore Tailings and Barrel Waste alternative —

a. Noise Analysis, a Tetra Tech memo dated January 15, 2010

b. Traffic Analysis, a Tetra Tech memo dated January 9, 2010

c. Geochemical Characterization of Facilities, a Tetra Tech memo dated January 10, 2010

d. Lighting, an M3 memo dated January 2010

6. Partial Backfill alternative —

a. Noise Analysis, a Tetra Tech memo dated January 23, 2010

b. Traffic Analysis, a Tetra Tech memo dated January 9, 2010

c. Geochemical Characterization of Facilities, a Tetra Tech memo dated January 10, 2010

7. Geochemical Pit Lake Predictive Model, prepared by Tetra Tech and dated February 2010

As per your request, I am transmitting three hardcopies and two disks (disks contain tech memos only) directly to the Forest Service and two copies and one disk directly to SWCA. The Pit Lake report includes

a copy of the report on a CD on the inside of the back cover of each report.