March 24, 2020 Ron Stenson, Senior Project Officer Uranium Mines and Mills Division 280 Slater Street P.O. Box 1046, Station B Ottawa, Ontario K1P 5S9 Dear Mr. Stenson: Re: Serpent River Watershed Monitoring Program – Year Five of Cycle 4 Denison Mines Inc. and Rio Algom Limited are pleased to submit one copy of the Serpent River Watershed Monitoring Program Year Five of Cycle 4 Annual Water Quality Report for 2019. If you have any questions or comments, please do not hesitate to contact the undersigned. Yours very truly, Denison Mines Inc. Rio Algom Limited Wade Wiggins, David Hewitt, Manager of Environmental Services Secondment Site Superintendent Elliot Lake cc: Distribution List Joint Review Group for the Serpent River Watershed Monitoring Program Rev 2020.02 Canadian Nuclear Safety Commission Ministry of Energy, Northern Development and Ron Stenson, Senior Project Officer Mines Uranium Mines and Mills Division Rob Purdon, Mine Rehabilitation Project Manager [email protected] Tel: 613-995-2624 [email protected] Tel: 807-631-8519 cc: [email protected] Mailing address: Mailing address: Ministry of Energy, Northern Development and Mines Canadian Nuclear Safety Commission 435 James Street South, Suite B002 280 Slater Street, P.O. Box 1046, Station B Thunder Bay, ON P7E 6S7 Ottawa, ON K1P 5S9 Environment and Climate Change Canada Environment and Climate Change Canada Catalin Obreja Duck Kim Physical Science Officer, Physical Science Officer, Environmental Stewardship Branch Environmental Stewardship Branch [email protected] Tel: 416-739-5973 [email protected] Tel: 416-739-5919 Mailing address: Mailing address: Environment Canada, Environment Canada, Environmental Protection Operations Environmental Protection Operations 4905 Dufferin Street, 2nd Floor, Office 2S316 4905 Dufferin Street, 2nd Floor, Office 2S311 Toronto, Ontario M3H 5T4 Toronto, Ontario M3H 5T4 Ministry of the Environment, Conservation and Ministry of the Environment, Conservation and Parks Parks Kirk Crosson, Ed Snucins Senior Environmental Officer, Surface Water Specialist, Northern Region Sault Ste Marie Area Office [email protected] Tel: 705-698-5546 [email protected] Tel: 705-942-6392 Mailing address: Mailing address: Ministry of the Environment, Conservation and Parks Ministry of the Environment, Conservation and Parks 199 Larch Street, Suite 1201 70 Foster Drive, Suite 110 Sudbury, Ontario P3E 5P9 Sault Ste Marie, ON P6A 6V4 Ministry of Natural Resources and Forestry Ministry of Natural Resources and Forestry Jim Trottier Megan Becker Management Biologist, Blind River Field Office Lands & Waters Technical Specialist, [email protected] Tel: 705-356-3018 Sault Ste Marie District [email protected] Tel: 705-941-5104 Mailing address: Ministry of Natural Resources and Forestry Mailing address: 62 Queen Avenue, P.O. Box 190 Ministry of Natural Resources and Forestry Blind River, ON P0R 1B0 64 Church Street, Sault Ste. Marie, ON P6A 3H3 Ministry of Labour, Training and Skills Ministry of Labour, Training and Skills Development Development Pierre Lefebvre Jerry Wedzicha District Manager, Timmins Program Specialist – Electrical Mechanical, [email protected] Tel: 705-235-1907 Mining Health and Safety Program [email protected] Tel: 705-564-4109 Mailing address: Ministry of Labour, Training and Skills Development Mailing address: Ontario Government Complex D Wing Ministry of Labour, Training and Skills Development 5520 Highway 101 East, P.O. Bag 3050 Ontario Government Bldg South Porcupine ON P0N 1H0 159 Cedar Street, Sudbury, ON P3E 6A5 Additional Distribution List 2020 Rev 2020.02 City of Elliot Lake Elliot Lake Public Library Mayor Dan Marchisella City of Elliot Lake Mailing address: [email protected] Elliot Lake Public Library Tel: 705-848-2287 ext 2126 Pearson Plaza 40 Hillside Drive South Mailing address: Elliot Lake, ON P5A 1M7 City of Elliot Lake 45 Hillside Drive North Elliot Lake, ON P5A 1X5 Serpent River First Nation Township of the North Shore Chief Brent Bissaillion Mary Lynn Duguay [email protected] Tel: 705-844-2418 Clerk-Treasurer [email protected] Tel: 705-849-2213 x 25 Mailing address: Serpent River First Nation Mailing address: 195 Village Road, P.O. Box 14 Township of the North Shore Cutler, ON P0P 1B0 1385 Hwy 17, P.O. Box 108 Algoma Mills, ON P0R 1A0 Town of Spanish Mississauga First Nation Pam Lortie Keith Sayers CAO/Clerk-Treasurer Land and Natural Resources Manager [email protected] Tel: 705-844-2300 [email protected] Tel: 705-356-1621 Mailing address: Mailing address: Town of Spanish Mississauga First Nation 8 Trunk Road, P.O. Box 70 64 Park Road, P.O. Box 1299 Spanish, ON P0P 2A0 Blind River, ON P0R 1B0 BHP (Rio Algom Ltd.) Denison Mines Inc. Ben Hoskie David Cates [email protected] [email protected] Tel: 520-448-5865 Tel: 416-979-1991 Serpent River Watershed Monitoring Program 2019 Annual Water Quality Report Submitted to the Canadian Nuclear Safety Commission March 31, 2020 Rio Algom Limited and Denison Mines Inc. 2019 SRWMP Annual Water Quality Report Table of Contents List of Figures.................................................................................................................... iii List of Tables ..................................................................................................................... iii List of Appendices ............................................................................................................. iii 1 Introduction ............................................................................................................ 4 2 Methodology .......................................................................................................... 4 2.1 2019 Program Requirements .................................................................... 4 2.2 2019 Program Conformance ..................................................................... 7 2.3 Field Measurements .................................................................................. 7 2.4 Data Quality Objectives ............................................................................. 7 2.5 Changes in Analytical Methods ............................................................... 10 2.6 Reporting of Method Detection Limits ..................................................... 10 2.7 Data Screening and Assessment Conventions ....................................... 10 3 Results ................................................................................................................ 10 3.1 Data Quality Results and Assessment .................................................... 10 3.2 2019 Annual Average Location Results Summary .................................. 14 3.3 Five-Year Annual Average Trends at Key Locations 2015-2019 ............ 15 4 Discussion ........................................................................................................... 18 4.1 Response Monitoring ............................................................................... 18 4.2 SRWMP Performance Monitoring Program Changes ............................. 18 4.3 Changes to Location Classification and Frequency ................................ 18 4.4 Interim Assessment in Support of Representative Public Radiation Dose Estimation ...................................................................................... 19 REFERENCES ................................................................................................................ 20 Page ii Rio Algom Limited and Denison Mines Inc. 2019 SRWMP Annual Water Quality Report LIST OF FIGURES Figure 2.1 Serpent River Watershed Water Quality Monitoring Locations ................. 6 Figure 3.1.a. Annual Average Sulphate Concentrations at SR-01, SR-06, SR-08, and DS-18, 2015-2019 ............................................................................ 17 Figure 3.1.b. Annual Average Radium Concentrations at SR-01, SR-06, SR-08, and DS-18, 2015-2019 ................................................................................... 17 Figure 3.1.c. Annual Average Uranium Concentrations at SR-01, SR-06, SR-08, and DS-18, 2015-2019 ............................................................................ 18 LIST OF TABLES Table 2.1 2019 SRWMP Water Quality Monitoring Requirements ............................ 5 Table 2.3 SRWMP Field Equipment Models and Accuracy ...................................... 7 Table 2.4.a. 2019 SRWMP Field Data Quality Objectives ............................................ 8 Table 2.4.b. 2019 SRWMP Laboratory Methods and Data Quality Objectives ................ 9 Table 3.1 2019 SRWMP Field Quality Control Results Summary ........................... 13 Table 3.2 2019 SRWMP Location Annual Average Results Summary ................... 16 LIST OF APPENDICES APPENDIX I Performance Monitoring Changes 2015 - 2019, Evolution of Programs APPENDIX II Flagged Data Results APPENDIX III Laboratory QA/QC Results APPENDIX IV Field QA/QC Results APPENDIX V Location Results APPENDIX VI Interim Public Dose Estimation for the Closed Mines of the Serpent River Watershed Page iii Rio Algom Limited and Denison Mines Inc. 2019 SRWMP Annual Water Quality Report 1 INTRODUCTION As part of the closure and decommissioning process, Rio Algom Limited (RAL) and Denison Mines Inc. (DMI) developed a focused and integrated performance monitoring network for legacy sites within the Serpent River Watershed (SRW). The comprehensive monitoring