c.o. Bmwner Engineering DU.

C O N S U I I I N C CI 01 rCIiNI CAI 1 NCINI.IIIINC

215 - 530 Raven Woods DriveNorth Vancouver, British Columbia Canada V7G 2T5Tel (604) 980-6189 F.:Ix (604) 980-6186email: cobrawnerë'shawcablo.corn

Review Report

Plan de Déposition - Parc à Résidus

Osisko Canadian Malartic Project

November 2008

Table of Contents

1.0 Introduction2.0 Design Concept by Golder3.0 Confirmation ofDesign Concept4.0 Further Geotechnical and Design Considerations

4.1 Tailings Properties4.2 Stability of the Tailings Pile4.3 Waste Rock Dike4.4 Influence ofClimate

5.0 Review

List of FiguresGeneral Aerial ViewFinal Modelled Configuration of the Tailings AreaWatershed locationsDike raise Schematic Typical Cross-section

Page

112233333

XlX2X3X4

c.o. Brawner Engineering lID.

eONSUlllNC C~OlFCIINICAI rNCINrEIIINC

215 - 530 Raven Woods DriveNorth Vancouver, Brilish Columbia Canada V7G 2T5Tel (604) 980-6189 Fax(604) 980-6186email: cobrawner@shawcable.com

Osisko Exploration2140 Rue St. MathieuMontreal, QuebecH3H 2J4

Attn: Paul Johnson, Ing.Manager, Mining

November 24, 2008

Re - Peer Review - Canadian Malartic ProjectPlan de Déposition - Parc à Résidus

Dear ML Johnson.

1.0 Introduction

Further to your request 1have reviewed the report "Plan de Déposition, Parc àRésidus de la Mine Canadian Malartic, Revision 1," by Golder Associates. 1wasalso provided with four figures from an earlier Golder Report - figures X-1, X-2,X-3 and X-4, which are attached.

2.0 Design Concept by Golder

The preliminary plan envisions depositing tailings thickened to 68% solids. At thisthickness the tailings flow to a steeper angle than typical tailings.

To develop an overall downstream slope of 10% it is proposed to constructintermediate dikes of waste rock. See figure X-4. The waste rock dikes of non­acid- generating waste rock will be 4 metres high with a 5.Cm wide berm.Thickened tailings will be deposited from several different discharge locations,

Collection and diversion ditches for the overflow water and seepage will bedeveloped outside the lowest waste rock dikes.

1

The design has been developed using Walace Software from the WruffwareCompany as weil as the Surpac program as a visualization tool. The topographyand volumes have been provided by Osisko. The surface topography is based ona grid of 20 x 20m. The height of the waste rack retaining dikes will be 4m.

The waste rock dump will be raised in advance of the tailings pile. The tailingstorage will encroach on the original tailings pond and sedimentation basin. Atthis time no geotechnical evaluation to assess the shear strength, stability orconsolidation characteristics has been performed to assess foundation conditionsfor the proposed tailings storage. This is required.

Water displaced by the tailings storage will be deposited in the new polishingpond. Water freed from the tailings and run-off water will be collected in a systemof collector ditches. A peripheral ditch will be constructed and will drain into thepolishing pond.

On mine c1osure, the surface of the exposed tailings will be progressivelycovered with Sm of mine waste rock from the waste dump.

3.0 Confirmation of Design Hypothesis

During active mining the following stages can be carried out to confirm the designhypothesis:

- Develop a test program on site at the start-up of the plant to verify thehypothesis of development - slopes, density in place, performance ofthe deposition system and other parameters as weil as developing themodel to reality. The verification is usually done by perforrninq detailedfield surveys to compare the results with the modal. Necessaryadjustments are then made to the model and the performance of sitedrainage can be verified if required.

- The stability of the entire pile must be verified to conform to thenumerical model and the hypotheses that have been used in thepreliminary design.

4.0 Further Geotechnical and Design Considerations

There are several important design and construction issues that need to beaddressed to confirm the proposed design model. These include the following:

4.1 Tailings Properties

a) Determination of the gradation and engineering properties of the tailings.Engineering properties to include moisture-density relationship, shearstrength and consolidation characteristics.

b) Permeability and drainage characteristics. Consideration of dump under­drainage. Will the tailings flow into voids of the waste rock pile?

2

c) Surface slope angle of the tailings for various flow rates.d) Trafficability for various types of construction equipment.

4.2 Stability of the tailings pile

a) Adequacy of the old tailings pond and sedimentation ponds asfoundations.

b) Seismic stability - earthquake and blasting.

4.3 Waste rock dike

a) Compatibility of tailing gradation with dike rock gradation. Require a filtercloth?

b) Constructability - equipment and procedure.

4.4 Influence of Climate

a) Summer conditions - heavy rainfall, high winds (dust)b) Winter conditions - frost heave, spring thaw effects.

5.0 Review

When the design reaches a final draft 1would be available to provide a reportreview.

C. O. Brawner, P. Eng.FCAE, FEIC, FCIM

3

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GENERAL VIEW

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WATERSHED LOCATIONS

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Distance ln melers

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FIGUIE

DYKE RAISESCHEMATIC TYPICAL CROSS-SECTION X.4