CÔTÉ GOLD PROJECT Chester and Yeo Townships, Ontario ENVIRONMENTAL EFFECTS REVIEW REPORT Submitted by: IAMGOLD Corporation 401 Bay Street, Suite 3200 Toronto, Ontario M5H 2Y4 September 2018 EXECUTIVE SUMMARY INTRODUCTION AND ENVIRONMENTAL EFFECTS REVIEW CONTEXT IAMGOLD Corporation (IAMGOLD) is a leading mid-tier gold producer headquartered in Toronto, Ontario. IAMGOLD is listed on the Toronto Stock Exchange main board under the symbol "IMG". IAMGOLD currently has four operating gold mines (including one joint venture) in Canada and abroad, and is in the process of developing additional projects, including the Côté Gold Project (the Project). IAMGOLD acquired Trelawney Mining and Exploration Inc. (Trelawney) in 2012. Trelawney had been exploring the Project property since 2009, with the objective of developing an open pit gold mine and process plant. As of December 31, 2015, the Côté Gold drill hole database contains results of 536 diamond drill holes for a total of 273,475. IAMGOLD has also undertaken or commissioned environmental, hydrogeological, geotechnical, mineralogical, engineering, logistics and economic studies related to the potential development of the property. Project Name: Côté Gold Project Proponent: IAMGOLD Corporation Primary Contact: IAMGOLD Corporation: Steven Woolfenden, Director, Environment 401 Bay Street, Suite 3200 Toronto, Ontario, M5H 2Y4 [email protected] Telephone: 416-594-2884 IAMGOLD submitted a Project Description to the Canadian Environmental Assessment Agency (CEAA) on March 15, 2013. Based on the Project Description, CEAA determined that a Federal Environmental Assessment (EA), pursuant to the Canadian Environmental Assessment Act, 2012 (CEAA 2012), was required. CEAA then issued draft Environmental Impact Statement (EIS) Guidelines on May 13, 2013 for review by federal departments, Indigenous groups and the Côté Gold Project Environmental Effects Review Report September 2018 EAB: EA 05-09-02; EAIMS: 13022; CEAA: 80036 Page ES-1 public. On July 9, 2013, the final EIS Guidelines were issued by CEAA outlining the scope of the EIS required for the Project. IAMGOLD entered into a Voluntary Agreement with the Ontario Ministry of the Environment (later renamed the Ministry of the Environment and Climate Change (MOECC)) on May 3, 2013 to conduct a Provincial Individual EA for the Côté Gold Project. The Provincial EA process was then initiated through the submission of a Draft Terms of Reference (ToR), to facilitate ongoing public consultation on the Project. A Draft ToR was issued for a 30-day public review comment period between May 10, 2013 and June 9, 2013. The Draft ToR was subsequently revised, based on comments on the document and results of open houses, and was re-issued as the Proposed ToR for another 30-day public comment review period from July 19, 2013 and August 19, 2013. The Proposed ToR was approved by the Ontario Minister of the Environment on January 14, 2014. The EIS / Draft EA report was prepared in accordance with the Proposed ToR and final EIS guidelines and was available for public review from June 13, 2014 to July 14, 2014. Comments received on the EIS / Draft EA report were addressed and incorporated into the Amended EIS / Final EA Report, which was submitted on February 20, 2015, hereafter defined as “the EA”. IAMGOLD received the EA decision statement of approval issued by the Federal Minister of Environment and Climate Change Canada on April 13, 2016 and received a statement of approval from the Ontario Ministry of the Environment and Climate Change on December 22, 2016. Following the receipt of the EA approvals for the Project, IAMGOLD has identified various opportunities to optimize the Project. IAMGOLD has also continued to review comments and feedback from First Nations and Métis, local communities, technical experts and government regulators. IAMGOLD also conducted a pre-feasibility study that assessed different options and has improved the Project economics, engineering, socio-economic benefits and reduced potential environmental effects. To ensure changes to the Project design are well communicated to government regulators, the public and Indigenous communities, and in accordance with Federal and Provincial EA Conditions of Approval, IAMGOLD has undertaken an environmental effects review (EER) to evaluate the potential effects of changes resulting from the optimization of the Project compared to the EA. Côté Gold Project Environmental Effects Review Report September 2018 EAB: EA 05-09-02; EAIMS: 13022; CEAA: 80036 Page ES-2 Key refinements that were made to the Project during the optimization process are presented in Table ES-1, and include: • A reduction in the Project footprint, specifically of the open pit, mine rock area (MRA) and Tailings Management Facility (TMF); • reduction in key operating parameters, including the mining rate and maximum annual movements of ore, overburden and mine rock, and the total ore, overburden and mine rock over the life of the mine; • relocation of the TMF nearer to the open pit, and no longer overprinting Bagsverd Creek; and • reduction in power requirements which removes the need for the cross-country 230 kV transmission line from Timmins. Table ES-1 Key Project Optimizations Component Previous Project Design Current Project Design (EA) (EER) Total Footprint 1,700 hectares (ha) 1,050 ha Life of Mine 15 years 17 years Open Pit and Ore Processing Footprint 210 ha 145 ha Ore Processing Rate 60,000 tonnes per day (tpd) 36,000 tpd Ore 261 million tonnes (Mt) 196 Mt Mine Rock Area Footprint 400 ha 300 ha Quantity 850 Mt 559 Mt Tailings Management Facility Location North of open pit (overprinting Northwest of open pit portions of Bagsverd Creek) Footprint 840 ha 478 ha Storage Capacity 261 Mt 200 Mt Maximum Dam Height 45 metres (m) 70 m Water Discharge Location Bagsverd Creek Three Duck Lakes (Upper) Camp Location Northwest of Open Pit Between Three Duck Lakes and Bagsverd Lake Overburden Stockpile Integrated in Mine Rock Area Southwest of Open Pit Watercourse Realignments 7.9 km (7 realignments) 2.4 km (2 realignments) Transmission Line Alignment 230 kilovolt (kV) cross-country Existing Hydro One Line from Alignment from Timmins Timmins to Shining Tree and (approximately 120 km) 115 kV transmission line alignment from Shining Tree (44 km) Côté Gold Project Environmental Effects Review Report September 2018 EAB: EA 05-09-02; EAIMS: 13022; CEAA: 80036 Page ES-3 PROJECT OVERVIEW IAMGOLD proposes to construct, operate and eventually rehabilitate a new open pit gold mine. The Project is located in the Chester and Yeo Townships in the District of Sudbury, in northeastern Ontario. It is approximately 20 kilometers (km) southwest of Gogama, 130 km southwest of Timmins, and 200 km northwest of Sudbury (see Figure ES-1). The Project site layout (see Figure ES-2) places the required mine-related facilities in close proximity to the open pit to the extent practicable, and on lands that are held fully and / or jointly by IAMGOLD. Ore processing will occur up to a rate of approximately 36,000 tpd. Overburden, mine rock and ore extracted from the open pit will be stockpiled in the overburden stockpile, MRA and ore stockpile, respectively. The Project footprint will cover approximately 1,050 ha (10.5 km2), excluding the transmission line alignment footprint (TLA). Ore processing will be carried out by conventional methods, using a combination of gravity separation and cyanidation for gold recovery, followed by in- plant cyanide recycling and destruction. Tailings will be stored in a constructed TMF. Water will be supplied to the ore processing plant from the mine water pond, the Reclaim Pond and Mesomikenda Lake. Site water will be discharged to Three Duck Lakes (Upper) via a Polishing Pond and / or following additional water treatment, if required. Discharge will meet applicable Federal and Provincial effluent discharge requirements and will be protective of aquatic life and receiving waters. Mining operations will be supported by the development of an explosives manufacturing and storage facility. A maintenance garage, warehouse and administration complex will be developed adjacent to the ore processing plant. An on-site accommodations complex will be developed at the start of construction with a capacity to host 1,000 to 1,200 workers. This complex will provide accommodation for the construction and operations workforce, some of which may commute from Gogama and from the Mattagami First Nation reserve. Potable water will be extracted primarily from groundwater resources. Côté Gold Project Environmental Effects Review Report September 2018 EAB: EA 05-09-02; EAIMS: 13022; CEAA: 80036 Page ES-4 IAMGOLD intends to deposit non-hazardous waste in a nearby off-site landfill currently operated by the Ministry of Natural Resources and Forestry (MNRF). The MNRF has been conducting a capacity study on the existing landfill to see if it will meet Project requirements and the future requirements of the existing local residences, and the permitting process for expansion is currently underway. IAMGOLD is planning to continue expanding its existing recycling program with the aim to minimize solid wastes. Domestic sewage will be treated using a sewage treatment plant. Hazardous solid and liquid waste will be hauled off site by licensed contractors to licensed disposal facilities. Opportunities to recycle some of the hazardous waste, such as used oil, will be investigated. Initial power for construction will be provided by the existing transmission line connection to the Provincial electrical grid, supported by diesel power generator(s) (less than 5 MW). Permanent power for the Project will be supplied by refurbishment of an abandoned 115 kV circuit between the Timmins Transformer Station (TS) and Shining Tree Distribution Station (DS) operated by Hydro One Networks Inc. (Hydro One), and a new 115 kV transmission line from the Shining Tree DS to the mine using an existing Hydro One right-of-way (ROW). To accommodate development of the open pit, Côté Lake will need to be dewatered and water bodies near the open pit will need to be dammed and / or realigned.