Environment & Safety

Safety

We manage the safety of our workers through programs, systems, and standards, with our Safety, Health, Environment and Quality (SHEQ) Policy providing overarching guidance. There are many aspects of the management system that contribute to a safe work environment, a few examples include:

Risk assessments help identify issues and determine the appropriate controls; the corrective action process verifies that incidents and near misses are reported, tracked, investigated and shared with colleagues; and emergency preparedness and planning prepare us to respond to serious incidents.
We have developed 12 corporate safety standards to help protect our workers from our most common hazards. Some standards guide our general safety practices, such as our job hazard analysis and our job task observation, and other standards deal with specific hazardous situations (similar to other companies’ life saving rules): such as fall protection, confined space entry, rigging and hoisting, and control of hazardous energy (also referred to as lockout/tagout).
Routine audits are conducted to monitor compliance with regulations and our own requirements. These and other aspects of the management system are routinely examined to verify that they continue to be effective at keeping our workers safe.

Radiation Protection

Radiation risks are effectively managed at McArthur River and Key Lake. Each operation has a formal radiation protection program and dedicated personnel who ensure that doses to workers are as low as reasonably achievable. The programs require that radiation protection is considered in the physical design of all facilities and operating procedures. They also provide for systematic monitoring of radiation in work areas and track exposures of individual workers using a combination of monitoring devices and health testing. Radiation exposures at McArthur River and Key Lake are far below below the regulated limits.

Environmental Protection

At Cameco, protection of the environment is one of our highest corporate priorities during all stages of our activities, from exploration through development, operations, decommissioning, and reclamation.

We monitor our performance by tracking corporate and site-specific key performance indicators, conducting environmental monitoring programs, and regularly auditing our adherence to the requirements of these programs We use the information from all of our programs to help us to identify opportunities to improve.

Environmental management system

We have a ISO 14001-certified environmental management system used across our operating sites, which is supported by a corporate Environmental Management Program that outlines the operating requirements sites must meet. Our environmental management system encourages and promotes continuous adaptation of our practices based on new information and technologies.

Environmental risk assessments

We complete environmental risk assessments to systematically identify, quantify, and to characterize the potential risks to the environment, workers, and the public. We use our environmental risk assessments to inform our decisions and actions. Additionally, we complete an iterative process, where required, to verify that our proposed measures to protect the environment and the public are effective. We review or update the assessments every five years, incorporating results from our environmental monitoring programs and other scientific advances.

Environmental performance reports

For our Saskatchewan operations, every five years we also compare monitoring data collected during the reporting period against predictions contained in approved environmental risk assessments or environmental assessments. By reviewing the data from the performance reports and conducting risks assessments, we are able to demonstrate that human health and the environment in the vicinity of our Saskatchewan operations remains protected. Results from these analyses are also used to inform changes to the environmental monitoring programs conducted at each operation.

Corrective action process

We have a corrective action process in place to systematically investigate and address the causes of non-conformance to regulatory requirements or internal standards. The process includes classifying the non-conformance, assigning the appropriate level of investigation (dependent on incident significance), and tracking the recommended corrective actions to prevent and mitigate similar occurrences.

Audits

To support our culture of continuous improvement, our processes and operations undergo regular audits, including:

Our environmental management system is audited by a third-party every three years as a requirement to maintain our ISO 14001 certification.
Our SHEQ team conducts an internal audit of our SHEQ programs on a three-year cycle. The total audit scope is split in half and executed on a rotating basis. This means that all our sites undergo at least two audits to cover all aspects of our SHEQ programs within every three-year period. The audit follows the ISO 19001 process and encompasses our environmental and safety programs.
We also maintain and implement an internal audit program at our corporate office. Results and recommendations from this systematic and documented process are presented to senior management, who are responsible for implementing them and correcting any deficiencies. The internal audit group reports to the audit and finance committee of the board.

Environmental Monitoring

Comprehensive monitoring programs are in place at the McArthur River and Key Lake operations to help ensure that the surrounding environment is protected. Samples of water, air, soil, plants and fish are collected from numerous locations around the sites and tested to confirm that environmental protection systems are effective. Monitoring results are submitted to federal and provincial regulatory authorities for review. Cameco also supports independent regional monitoring downstream of its Saskatchewan operations to ensure there are no cumulative effects on the regional watershed. The extensive monitoring undertaken at McArthur River and Key Lake has identified no significant impact on the surrounding environment.

McArthur River Monitoring Results

Treated Water Quality — Arsenic
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3
McArthur River Level (mg/L)	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0002	0.0003	0.0004	0.0002	0.0004	0.0003

Key Lake Monitoring Results

Treated Water Quality — Arsenic NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3
Key Lake Level (mg/L)	0.0110	0.0298	0.0215	0.0079	0.0061	0.0078	0.0015	0.0009	0	0	0	0	0	0.0025	0.0011	0.0032	0.0025	0.0014	0.0014	0.0026	0.0020	0.0018	0.0015	0.0019

McArthur River Monitoring Results

Treated Water Quality — Copper
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3
McArthur River Level (mg/L)	0.0004	0.0003	0.0002	0.0002	0.0003	0.0005	0.0004	0.0006	0.0005	0.0005	0.0004	0.0003	0.0005	0.0012	0.0008	0.0009	0.0007	0.0008	0.0010	0.0008	0.0009	0.0023	0.0006	0.0007

Key Lake Monitoring Results

Treated Water Quality — Copper NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3
Key Lake Level (mg/L)	0.0057	0.0052	0.0018	0.0009	0.0005	0.0005	0.0005	0.0003	0	0	0	0	0	0.0013	0.0008	0.0018	0.0036	0.0022	0.0037	0.0069	0.0042	0.0034	0.0067	0.0048

McArthur River Monitoring Results

Treated Water Quality — Lead
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
McArthur River Level (mg/L)	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0001	0.0002	0.0001	0.0001	0.0001	0.0001

Key Lake Monitoring Results

Treated Water Quality — Lead NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Key Lake Level (mg/L)	0.0010	0.0009	0.0001	0.0003	0.0002	0.0004	0.0021	0.0006	0	0	0	0	0	0.0005	0.0006	0.0003	0.0002	0.0001	0.0001	0.0001	0.0001	0.0002	0.0001	0.0001

McArthur River Monitoring Results

Treated Water Quality — Nickel
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
McArthur River Level (mg/L)	0.0020	0.0017	0.0021	0.0022	0.0024	0.0025	0.0032	0.0016	0.0013	0.0020	0.0017	0.0016	0.0012	0.0017	0.0017	0.0031	0.0036	0.0027	0.0021	0.0018	0.0017	0.0028	0.0012	0.0011

Key Lake Monitoring Results

Treated Water Quality — Nickel NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Key Lake Level (mg/L)	0.1180	0.0768	0.1202	0.1200	0.0788	0.0542	0.0844	0.0300	0	0	0	0	0	0.1160	0.1185	0.0665	0.0530	0.0575	0.0456	0.0285	0.0365	0.1360	0.0838	0.0870

McArthur River Monitoring Results

Treated Water Quality — Zinc
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
McArthur River Level (mg/L)	0.0020	0.0016	0.0016	0.0023	0.0020	0.0024	0.0027	0.0016	0.0011	0.0016	0.0012	0.0021	0.0015	0.0026	0.0024	0.0021	0.0035	0.0024	0.0024	0.0038	0.0026	0.0054	0.0021	0.0034

Key Lake Monitoring Results

Treated Water Quality — Zinc NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Key Lake Level (mg/L)	0.0076	0.0080	0.0040	0.0057	0.0036	0.0034	0.0042	0.0027	0	0	0	0	0	0.0048	0.0052	0.0045	0.0031	0.0020	0.0019	0.0018	0.0027	0.0034	0.0032	0.0045

McArthur River Monitoring Results

Treated Water Quality — Suspended Solids
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15
McArthur River Level (mg/L)	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0

Key Lake Monitoring Results

Treated Water Quality — Suspended Solids NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15	15
Key Lake Level (mg/L)	1	2	1	1	1	1	1	2	0	0	0	0	0	2	2	2	4	3	4	5	4	4	2	2

McArthur River Monitoring Results

Treated Water Quality — Radium-226
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (Bq/L)	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37
McArthur River Level (Bq/L)	0.040	0.032	0.028	0.023	0.022	0.028	0.023	0.020	0.020	0.013	0.018	0.028	0.028	0.036	0.023	0.024	0.035	0.040	0.050	0.068	0.073	0.045	0.048	0.100

Key Lake Monitoring Results

Treated Water Quality — Radium-226 NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (Bq/L)	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37	0.37
Key Lake Level (Bq/L)	0.013	0.044	0.031	0.019	0.010	0.005	0.040	0.010	0	0	0	0	0	0.009	0.015	0.015	0.014	0.013	0.009	0.006	0.009	0.010	0.006	0.009

McArthur River Monitoring Results

Treated Water Quality — pH
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Authorized Maximum pH	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5
McArthur River Level pH	7.4	7.4	7.3	7.3	7.4	7.4	7.4	7.5	7.5	7.4	7.6	7.5	7.5	7.5	7.5	7.3	7.2	7.3	7.3	7.5	7.3	7.1	7.1	7.1
Authorized Minimum pH	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0

Key Lake Monitoring Results

Treated Water Quality — pH NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Authorized Maximum pH	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5	9.5
Key Lake Level pH	6.9	6.9	7.0	7.0	7.0	7.1	7.1	6.9	0	0	0	0	0	6.9	7.0	7.3	7.5	7.3	7.2	6.9	7.1	7.4	7.2	7.0
Authorized Minimum pH	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0	6.0

McArthur River Monitoring Results

Treated Water Quality — Selenium
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Saskatchewan Ministry of Environment Limit (mg/L)	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6
McArthur River Level (mg/L)	0.0003	0.0003	0.0002	0.0003	0.0002	0.0002	0.0002	0.0003	0.0003	0.0002	0.0003	0.0003	0.0003	0.0004	0.0004	0.0008	0.0013	0.0025	0.0015	0.0031	0.0039	0.0016	0.0035	0.0047

Key Lake Monitoring Results

Treated Water Quality — Selenium NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Saskatchewan Ministry of Environment Limit (mg/L)	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6
Key Lake Level (mg/L)	0.0082	0.0094	0.0112	0.0108	0.0102	0.0102	0.0097	0.0099	0	0	0	0	0	0.0088	0.0086	0.0086	0.0082	0.0096	0.0096	0.0117	0.0116	0.0084	0.0132	0.0130

McArthur River Monitoring Results

Treated Water Quality — Uranium
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Saskatchewan Ministry of Environment Limit (mg/L)	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5
McArthur River Level (mg/L)	0.0048	0.0090	0.0040	0.0050	0.0148	0.0111	0.0184	0.0175	0.0121	0.0083	0.0094	0.0048	0.0024	0.0095	0.0064	0.0179	0.0054	0.0139	0.0092	0.0309	0.0072	0.0105	0.0042	0.0030

Key Lake Monitoring Results

Treated Water Quality — Uranium NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Saskatchewan Ministry of Environment Limit (mg/L)	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5
Key Lake Level (mg/L)	0.0227	0.0213	0.0366	0.0364	0.0199	0.0107	0.0181	0.0099	0	0	0	0	0	0.0205	0.0304	0.0433	0.0346	0.0078	0.0061	0.0046	0.0029	0.0175	0.0013	0.0015

McArthur River Monitoring Results

Treated Water Quality — Molybdenum
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
McArthur River Level (mg/L)	0.0142	0.0182	0.0114	0.0070	0.0049	0.0031	0.0027	0.0116	0.0046	0.0037	0.0120	0.0070	0.0077	0.0149	0.0198	0.0456	0.0830	0.0640	0.0688	0.1705	0.1325	0.1646	0.1883	0.1205

Key Lake Monitoring Results

Treated Water Quality — Molybdenum NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Jul-21	Aug-21	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Key Lake Level (mg/L)	0.0730	0.0697	0.1510	0.0196	0.0225	0.0141	0.0035	0.0016	0	0	0	0	0	0.0282	0.0052	0.0153	0.0153	0.0096	0.0363	0.0282	0.0647	0.0714	0.0352	0.0720

McArthur River Monitoring Results

Treated Water Quality — Un-ionized Ammonia as Nitrogen
	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
McArthur River Level (mg/L)	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01

Key Lake Monitoring Results

Treated Water Quality — Un-ionized Ammonia as Nitrogen NOTE: No reporting for Mar-Jul 2022 as facility down for scheduled maintenance.
	Sep-21	Oct-21	Nov-21	Dec-21	Jan-22	Feb-22	Mar-22	Apr-22	May-22	Jun-22	Jul-22	Aug-22	Sep-22	Oct -22	Nov-22	Dec-22	Jan-23	Feb-23	Mar-23	Apr-23	May-23	Jun-23
Metal and Diamond Mining Effluent Regulations (mg/L)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Key Lake Level (mg/L)	0.01	0.01	0.01	0.01	0.01	0.01	0	0	0	0	0	0.01	0.01	0.01	0.02	0.03	0.03	0.03	0.03	0.11	0.08	0.08

McArthur River Monitoring Results

Ambient Air Quality – Annual Average Total Suspended Particulate (TSP)
*NOTE - Regulations replaced and standard revised on June 1, 2015; however for consistency, the old value is referenced for the 2015 reporting year. Reporting against the new value began in Q1 2016.*
	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023 Q2
Saskatchewan Ministry of Environment Standard - see note (µg/m³)	70	70	70	70	60	60	60	60	60	60	60	60
Annual Average (µg/m³)	7.2	4.9	4.2	4.2	2.3	3.2	1.7	1.4	1.1	2.2	2.7	3.4

Key Lake Monitoring Results

Ambient Air Quality – Annual Average Total Suspended Particulate (TSP)
*NOTE - Regulations replaced and standard revised on June 1, 2015; however for consistency, the old value is referenced for the 2015 reporting year. Reporting against the new value began in Q1 2016.*
	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023 Q2
Saskatchewan Ministry of Environment Standard - see note (µg/m³)	70	70	70	70	60	60	60	60	60	60	60	60
Annual Average (µg/m³)	11.5	10.4	10.3	10.0	10.8	12.2	8.8	6.7	5.9	6.9	6.4	5.6

Key Lake Monitoring Results

Ambient Air Quality – Annual Average Ambient Sulfur Dioxide (SO₂)
*NOTE - Regulations replaced and standard revised on June 1, 2015; however for consistency, the old value is referenced for the 2015 reporting year. Reporting against the new value began in Q1 2016.* *During Care and Maintenance, the plant was shut down, therefore no emissions were reported.*
	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023 Q2
Saskatchewan Ministry of Environment Standard (ppb)	10	10	10	10	8	8	8	8	8	8	8	8
Annual Average (ppb)	7.7	6.7	7.3	9.1	0.5	0.4	0	0	0	0	0	0.3

Environmental Incidents and Other Events

Environmental incidents and other events are reported to regulatory agencies as required by federal and provincial regulations.

Latest incidents or events:

McArthur River

Date	July 10, 2023
Incident	Event Requiring Reporting to the Duty Officer
Details	During the annual field verification of all radioactive sources, site radiation staff were unable to locate one americium 241 check source that is included in the source inventory list. The source activity is below the exemption quantity. After reporting to the supervisor, a secondary search of the sealed source storage area was completed.
Corrective Action	The site is investigating whether the source was previously disposed or transferred and not removed from the inventory list.
Environmental Effect	1

Past reporting

McArthur River

Date	July 10, 2023
Incident	Event Requiring Reporting to the Duty Officer
Details	During the annual field verification of all radioactive sources, site radiation staff were unable to locate one americium 241 check source that is included in the source inventory list. The source activity is below the exemption quantity. After reporting to the supervisor, a secondary search of the sealed source storage area was completed.
Corrective Action	The site is investigating whether the source was previously disposed or transferred and not removed from the inventory list.
Environmental Effect	1

Date	June 22, 2023
Incident	Reportable Spill, Discharge, Discovery or Release
Details	Approximately 150 litres of contaminated liquid from the mine water treatment process were released to the ground adjacent to the Mine Water Treatment Plant. The amount released was confirmed to be well below the discharge quantity of 1000 L and was due to a leak in the filter system used to separate the solids from the mine water.
Corrective Action	The affected area was cleaned and the contaminated material was placed on a mineralized ore storage pad. A radiation scan of the area confirmed the release was fully cleaned. The maintenance department repaired the filter system and curtains were installed around the perimeter of the filter system.
Environmental Effect	1

Date	May 10, 2021
Incident	Reportable release
Details	An increase in outdoor temperatures caused snow meltwater to accumulate within utilidor sump #7 and approximately 2,000 liters of meltwater overflowed the sump onto the ground. This event is classified as a reportable release.
Corrective Action	An alternative pumping system has been set up. Provincial and federal regulators were notified.
Environmental Effect	1

Date	March 12, 2021
Incident	Fire alarm system activation
Details	The Emergency Response Team (ERT) responded to a fire alarm activation on the third floor east wing of the permanent camp.The Emergency Response Team (ERT) responded to a fire alarm activation on the third floor east wing of the permanent camp.
Corrective Action	The ERT team swept the area and determined the fire alarm activation was due to steam. Area was cleared to allow tradespeople to mitigate issue with assistance of ERT team members. Federal regulators were informed.
Environmental Effect	N/A

Date	February 8, 2021
Incident	Fire alarm system activation
Details	At approximately 12:30 p.m. the fire alarm system in the main camp was activated as a result of light smoke detected in the E-wing. In accordance with emergency procedures, camp residents reported to the designated muster point and the emergency response team (ERT) responded and verified that there was no fire. The cause of the observed smoke was determined to be a damaged belt on the air handling unit.
Corrective Action	The camp wing was ventilated and the belt was replaced. Once the area was verified as safe, the alarm system was reset. The CNSC has been notified and follow-up reporting will take place.
Environmental Effect	N/A

Date	September 18, 2020
Incident	Fire alarm system activation
Details	At approximately 12:30 p.m. a fire alarm was activated underground near the material delivery chute on the 640 level. The emergency response team (ERT) responded in accordance with emergency procedures and verified that there was no fire.
Corrective Action	An investigation into the cause of the false alarm is underway. The CNSC has been notified.
Environmental Effect	N/A

Date	July 29, 2020
Incident	Fire system activation
Details	The emergency response team (ERT), responded to fire system activation in the north-ex refuge station (530 level) underground. The ERT responded in accordance with emergency procedures and verified that there was no fire or smoke.
Corrective Action	Investigation indicated that high humidity levels caused a smoke detector to go into alarm. The CNSC was notified.
Environmental Effect	N/A

Cameco Environmental Effect Rating

Level 1 - no measurable impact to the environment
Level 2 - negligible impact
Level 3 - short-term, seasonal impact
Level 4 - mortality of some species, but not affecting ecosystem function
Level 5 - impairment of ecosystem function
N/A - not applicable

Key Lake

Date	September 12, 2023
Incident	Radiation Action Level Exceedance
Details	A worker performing maintenance in the mill area received a preliminary dose estimate indicative of a weekly action level exceedance.
Corrective Action	Confirmatory enhanced urine collection samples were analyzed at both Key Lake and Port Hope Conversation Facility (PHCF) labs and additional monitoring of the worker occurred at PHCF. Action level exceedance has been reported to the CNSC and an investigation is underway.
Environmental Effect	N/A

Past reporting

Key Lake

Date	September 12, 2023
Incident	Radiation Action Level Exceedance
Details	A worker performing maintenance in the mill area received a preliminary dose estimate indicative of a weekly action level exceedance.
Corrective Action	Confirmatory enhanced urine collection samples were analyzed at both Key Lake and Port Hope Conversation Facility (PHCF) labs and additional monitoring of the worker occurred at PHCF. Action level exceedance has been reported to the CNSC and an investigation is underway.
Environmental Effect	N/A

Date	September 6, 2023
Incident	Radiation Action Level Exceedance
Details	A worker performing maintenance on the primary thickener in the counter current decantation (CCD) mill area received a preliminary dose estimate indicative of a quarterly action level exceedance (estimate of greater than 5 mSv).
Corrective Action	Confirmatory enhanced urine collection samples were analyzed at both Key Lake and McArthur River labs. Action level exceedance has been reported to the CNSC and an investigation is underway.
Environmental Effect	N/A

Date	September 3, 2023
Incident	Reportable Spill, Discharge, Discovery or Release
Details	An operator was filling the water wagon at the industrial water fill station near the Mine shop. The operator removed the wheel chocks and started the engine to the water wagon prior to disconnecting the fill hose. The water wagon rolled back slightly, which resulted in damage to the industrial water line located within the feed utilidor. Approximately 1,200 m3 of industrial water was released inside the utilidor (secondary containment). An additional 12 m3 was released outside to the ground near the crusher sump.
Corrective Action	The valve for the fill station was closed and the industrial water line was isolated. Environment personnel collected samples. The water wagon was locked out for mechanical inspection. The proper fill procedures and use of wheel chocks were reviewed with site services personnel.
Environmental Effect	1

Date	August 16, 2023
Incident	Reportable Spill, Discharge, Discovery or Release
Details	After the leak detection alarm was activated, a leaking pipeline within the feed utilidor was discovered. The material was initially released to secondary containment within the feed utilidor. However, approximately 200 kg of uranium ore slurry was released to the ground through a small opening located between the utilidor lids. It was determined the leak was caused by the failure of a victaulic clamp on the pipeline.
Corrective Action	A gamma survey was completed. A vacuum truck cleaned up the material released to the ground and transported it to the ore pads.
Environmental Effect	1

Date	July 12, 2023
Incident	Event Requiring Reporting to the Duty Officer
Details	A fire started in the sulphur pit, which is a concrete structure built into the ground within the Key Lake Acid Plant. The Emergency Response Team responded and added 150 lb of dry chemical on the intake side of the pit to smother the fire and drop the temperature within the pit. Water was also added to further drop the temperature. No one was injured in the incident.
Corrective Action	The cause of the fire is under investigation and the area is being monitored.
Environmental Effect	1

Date	June 27, 2023
Incident	Event Requiring Reporting to the Duty Officer
Details	While laboratory staff were refilling squirt bottles, nitric acid (1%) was inadvertently mixed with chlorine bleach (10%). This mixture creates chlorine gas. Lab staff immediately alerted their supervisor and evacuated the area. The Emergency Response Team responded to the chemistry lab, performed gas testing and confirmed the area was safe.
Corrective Action	The mixture was properly disposed. While the bottles had the proper WHMIS labels, laboratory staff have implemented a visual check by adding color to the exterior of each bottle to further differentiate the chemicals.
Environmental Effect	N/A

Date	June 6, 2023
Incident	Dangerous Occurrence
Details	Workers were tasked with changing a motor on a pump in the secondary containment of the #1 and 2 Leach Pachuca's. The crane was test ran to ensure that it travelled North, South and up and down. While conducting the initial lift of the motor, the workers noticed that one side of the rollers on the Storage Pachua Chain Hoist trolley had shifted and became partially dislodged from the I-Beam. The workers immediately lowered the motor back down onto a secure platform and secured the crane with a chain hoist. There were no injuries as a result of this event. The motor being lifted was 475 pounds and the crane is rated for 1 tonne. The lift area was roped off prior to utilizing the crane, so there were no workers present in the area below.
Corrective Action	The incident scene was secured; crane was tagged out and then danger taped off to aid in the investigation of the incident and remove any risk to workers in that area. The OHC committee was convened on June 6, 2023, to investigate the event and ruled the incident a Dangerous Occurrence. Further investigation is currently under way.
Environmental Effect	N/A

Date	May 31, 2023
Incident	Event Requiring Reporting to the Duty Officer
Details	In the Mill Facility, an employee fell down the staircase in the yellowcake area, resulting in injuries to their shoulder, knee, elbow, and hand. The emergency response team provided initial assessment and treatment. The employee left on a regularly scheduled flight for an offsite assessment accompanied by an ERT member. It was determined the individual did not sustain any fractures.
Corrective Action	There were no issues noted with the staircase handrail and no tripping hazards were observed. Further investigation will be completed.
Environmental Effect	N/A

Date	April 25, 2023
Incident	Potential Radiation Action Level Exceedance
Details	A pinhole leak developed on the line between Continuous Stir Tank Reactors 4 and 6, inside the leaching circuit building. This resulted in leaching process material (slurry) intermittently spraying and potentially misting along the wall and walkway. Five individuals were working in the area and were contacted by the slurry mist. The preliminary dose estimates for two individuals indicated a potential weekly action level exceedance (estimate of greater than 1 mSv). Further analysis is required to confirm the dose calculations.
Corrective Action	The area was barricaded and cleaned up. The leak on the pipe was isolated and repairs were completed. Five individuals in the area completed Uranium in Urine sampling to evaluate the possibility for intake. Samples from two workers indicated potential for measurable dose. Enhanced U in U samples for these workers were shipped to Port Hope for analysis and confirmation of the results was received on May 10th.
Environmental Effect	N/A

Date	April 15, 2023
Incident	Event Requiring Reporting to the Duty Officer
Details	The emergency response team responded to and extinguished a small amount of saw dust that was observed smoldering in a waste bin outside the maintenance shop.
Corrective Action	The event was investigated and the cause is believed to be due to an overheated saw blade.
Environmental Effect	1

Date	April 15, 2023
Incident	Emergency Transport to External Medical Facilities / Dangerous Occurrence
Details	While working in the Crushing and Grinding building, a worker was struck by a phone booth unit that dislodged from its mounting brackets. The emergency response team was activated to provide medical care and transport to the site health centre. The worker was transported offsite in stable condition via air ambulance for further assessment.
Corrective Action	The incident scene was secured and all other similar phone booth structures at the operation have been taped off until further assessment can be completed. The OHC committee was convened to investigate the event.
Environmental Effect	N/A

Date	January 10, 2023
Incident	Radiation Action Level
Details	While performing maintenance on a leaching vessel, two workers had an unplanned radiation exposure that led to exceedances of the quarterly action level of 5 mSv. The total annual dose for both workers remains well below regulatory limits.
Corrective Action	The workers were removed from the their tasks to complete the follow-up investigation and dose assessment process. The remaining maintenance work on the leaching vessel was completed in accordance with the applicable procedure without incident.
Environmental Effect	1

Date	November 25, 2022
Incident	Reportable Discharge
Details	Around 3 a.m., technicians were installing a new helium cylinder in the Chemical Lab gas storage room. When removing the plastic safety cover from the new cylinder outlet valve, the helium began venting. The lab gas storage room was immediately evacuated and sealed off to allow the cylinder to safely vent. The discharge of the helium was approximately 30 minutes in duration, which exceeds the reportable discharge duration of less than 10 minutes.
Corrective Action	No entry to the gas storage room was allowed until the air monitoring system indicated it was safe. The cylinder was properly secured at the time of the release. It will be sent back to the manufacturer to investigate if the valve was defective.
Environmental Effect	2

Date	November 24, 2022
Incident	Regulatory Emission Limit Exceedance
Details	The Total Suspended Solids (TSS) regulatory emission limit of 30 mg/L for a grab sample collected from treated water was exceeded for a partial pond released at station 1.4, Bulk Neutralization Effluent discharge. Prior to release, analysis of the pond fill sample returned a TSS value that was acceptable for release. During release, the in-line turbidity monitoring interlock system was activated, halting the discharge. Additional samples were taken and returned results that were acceptable for release. Pond release resumed, however, the turbidity interlock system halted the release a second time, and the remainder of the pond was recycled back to Bulk Neutralization for treatment. The pond release sample was analyzed and returned a value of 37 mg/L, exceeding the regulatory emission limit for a grab sample. Approximately 32% (1307 m3) of the pond was released to the environment and 68% (2788 m3) was recycled.
Corrective Action	An additional sample was sent to the SRC Analytical Laboratory for further verification. A sample collected on November 25 from the nearest downstream sample location at Station 4.0 Wolf Lake, indicated normal TSS levels. Further investigation is currently underway.
Environmental Effect	2

Date	October 28, 2022
Incident	Environmental Action Level Exceedance
Details	In accordance with site procedures, a pond of treated effluent was released based on the results of the pond fill composite sample. Results for the pond release composite sample indicated the measured value for uranium (81 µg/L) exceeded the action level of 80 µg/l. Measured results for all parameters, including uranium, were well below the applicable regulatory limits. There was no health or safety risk posed to the public, workers or the environment.
Corrective Action	Cameco notified the Canadian Nuclear Safety Commission, and an investigation has been initiated.
Environmental Effect	2

Date	October 22, 2022
Incident	Reportable Release
Details	A line at Key Lake’s processing facility released water to the ground. It is believed the line was frozen, causing the release. 6 cubic metres of industrial water was released.
Corrective Action	Operations lowered the water level in a tank to prevent further overflow to the line. Environment was contacted to collect samples and Site Services used a vacuum truck to clean up the area. The material was disposed of on site.
Environmental Effect	2

Date	September 20, 2022
Incident	Reportable Release
Details	An estimated 2,000 litres of industrial wastewater from the mine shop pump bay sump were released on the ground when the pump testing pit overfilled with potable water. It was determined that when a hose was placed on the hose rack next to the fill valves, the potable water fill valve was bumped into the “on” position, resulting in the sump to fill and overflow.
Corrective Action	The supervisor was notified, and the fill valve was shutoff. The event was reported to the environment and site services departments for investigation and cleanup. Federal and provincial regulators were notified.
Environmental Effect	2

Date	July 13, 2022
Incident	Event Requiring Reporting to the CNSC Duty Officer
Details	The incident command centre has been activated in response to a fire southwest of Key Lake. The Key Lake site is not currently under immediate threat. The Saskatchewan Public Safety Agency (SPSA) crews continue to monitor closely.
Corrective Action	The SPSA continues to monitor and provide updates to site. The site re-established a fuel break at the VOR station located approximately 10 km southwest of Key Lake, at the direction of the SPSA.
Environmental Effect	N/A

Date	July 5, 2022
Incident	Radiation Action Level Exceedance
Details	Elevated monitoring sample measured for worker post CCD thickener maintenance. Preliminary dose estimate indicated a quarterly action level may have been exceeded. Further analysis was required to confirm dose calculations.
Corrective Action	All work was stopped in the area until initial investigation was completed. Workers convened for a JHA to discuss procedure for any work in the CCD thickener going forward. Samples were shipped to an external lab for confirmatory analysis.
Environmental Effect	N/A

Date	March 29, 2022
Incident	Reportable release
Details	At about 10:15 a.m., during daily inspection, ground water from Well V of the Gaertner dewatering system was observed in a small area outside the well shelter. Release volume is estimated at more than 1000 litres.
Corrective Action	The reverse osmosis plant feed was re-routed to an alternate well, isolating Well V from the dewatering system. Water samples were collected and site services conducted cleanup. Further investigation into the incident will be conducted after ground thaws. Provincial and federal regulators were notified.
Environmental Effect	1

Date	February 16, 2022
Incident	Reportable release
Details	At about 4:00 a.m., a propane leak was detected near the steam plant.
Corrective Action	A faulty propane line was isolated and the area secured. Cause of the line failure is under investigation. Provincial and federal regulators were notified.
Environmental Effect	1

Date	December 27, 2021
Incident	Reportable release
Details	At about 2:50 a.m., an alarm indicated a propane leak on propane pump #2, near the steam plant.
Corrective Action	The pump was isolated and the cause of the leak was determined to be a broken pipe fitting to the pressure gauge on the pump. The cause of the breakage is under investigation. Provincial and federal regulators were notified.
Environmental Effect	1

Date	September 20 and September 27, 2021
Incident	Unusual incidents
Details	The weekly effluent sample for the Reverse Osmosis (RO) effluent at Station 1.2 Discharge to Horsefly Lake was not collected on the above dates. Station 1.2.1 Horsefly Lake Outflow was mistakenly collected in place of the Station 1.2 Discharge to Horsefly Lake.
Corrective Action	The RO daily product sample results were reviewed, and all parameters analyzed on both days were confirmed to be below the Metal and Diamond Mining Effluent Regulation (MDMER) limits.
Environmental Effect	1

Date	September 13, 2021
Incident	Reportable release
Details	A propane leak was detected in a line outside of the CCD, near the Leaching facility. Corrosion to the piping was observed.
Corrective Action	Valve was closed and locked to stop the flow and repairs will be initiated. Provincial and federal regulators were notified.
Environmental Effect	1

Date	September 7, 2021
Incident	Event Requiring Reporting to the Duty Officer
Details	On September 7th, the Emergency Response Team was activated at 10:15am and responded to a non-work-related medical emergency involving a person working at the mill terrace reservoirs. The team was stood down at 10:55am.
Corrective Action	The Emergency Response Team responded and provided initial assessment and transported the worker in stable condition to the health centre for additional assessment and care.
Environmental Effect	N/A

Date	June 22, 2021
Incident	Reportable release
Details	Examination of 2020 and 2021 groundwater sampling results from new monitoring wells indicated elevated levels of parameters such as ammonia and sulfate below the mill terrace area.
Corrective Action	An assessment indicates the source is likely a release of water contaminated with barren strip solution. The release is believed to have occurred prior to the operation being placed into care and maintenance in 2018, as tests have indicated there is not an active discharge occurring. Further investigation is underway. Additional drilling and sampling will be completed to further assess groundwater conditions in this area. Inspections and repairs will be completed prior to resumption of production. Provincial and federal regulators were notified.
Environmental Effect	2

Date	April 18, 2021
Incident	Dangerous occurrence
Details	While decommissioning electrical cables in the packaging area, a 120V energized wire was inadvertently cut. This caused the breaker to trip and no injuries occurred.
Corrective Action	The electrical wire was repaired and an investigation is underway. Provincial and federal regulators were notified.
Environmental Effect	N/A

Date	February 12, 2021
Incident	Reportable release
Details	At around 8:15 a.m., a leak detection alarm in Valve Shelter #1 was activated after a damaged 3-inch pipe released approximately 3m³ of water to the floor of the shelter and outside the doorway. Upon investigation, it was determined that freezing temperatures had caused the pipe to split.
Corrective Action	A lateral valve in the shelter was closed, which stopped the release. The material was cleaned up utilizing a vacuum truck. The damaged pipe is being repaired. Provincial and federal regulators were notified.
Environmental Effect	1

Date	October 27, 2020
Incident	Reportable release
Details	At approximately 6:15 a.m., workers noted that a water supply line valve in the wash bay had been left open overnight resulting in the release of approximately 12,000 litres of water onto the frozen ground outside the building.
Corrective Action	Workers shut off the water supply valve. Water samples were collected for analysis and the slush/ice build-up on the frozen ground was removed for transfer to the Phase IV Ore Pad. Provincial and federal regulators were notified.
Environmental Effect	1

Date	March 17, 2020
Incident	Reportable release
Details	At approximately 2:30 p.m. in the reverse osmosis (RO) facility, the automated shutdown of water pumps failed resulting in the release of approximately 3,000 litres of dewatering water to the ground.
Corrective Action	All wells providing water to the RO plant were shut down. Released water, which froze in place on the ground, was removed and placed on the Gaertner special waste pad. Preliminary investigation indicates a system communication power loss, from a UPS failure during maintenance testing, resulted in loss of signal between the high water level alarm and automated pump shutdown system. Provincial and federal regulators were notified.
Environmental Effect	1

Date	March 8, 2020
Incident	Emergency response team (ERT) activation
Details	At 12:24 p.m., the emergency response team (ERT) responded to a burst fire system water line in the stairwell of the mine shop.
Corrective Action	Water was isolated and the line was repaired. ERT investigation revealed the line had frozen and burst due to cold weather and heating failure. Federal regulators were notified.
Environmental Effect	N/A

Cameco Environmental Effect Rating

Level 1 - no measurable impact to the environment
Level 2 - negligible impact
Level 3 - short-term, seasonal impact
Level 4 - mortality of some species, but not affecting ecosystem function
Level 5 - impairment of ecosystem function
N/A - not applicable

Decommissioning

Detailed plans and financial guarantees are in place to provide for decommissioning of the McArthur River and Key Lake sites when operations end. Decommissioning will include removal of all buildings and equipment and landscaping and re-vegetation of disturbed areas. All underground workings and other mine and mill facilities will be sealed off and secured. A monitoring program will be in place to ensure the sites remain in a secure and stable state for the long-term.

For more information, see:

Preliminary Decommissioning Plan - Summary - McArthur River Operation

Preliminary Decomissioning Plan - Summary - Key Lake Operation

Environmental Risk Assessment

All new, or substantially changed, mining developments may be subject to environmental risk assessments (ERAs) to identify potential effects on the environment. ERAs follow guidance provided by CSA and various agencies, such as Health Canada (HC), Environment and Climate Change Canada (ECCC), Canadian Council of Ministers of the Environment (CCME) and the Canadian Nuclear Safety Commission (CNSC).

In 2020, Cameco completed a detailed quantitative environmental risk assessments (ERA) for its McArthur River and Key Lake Operations to align with the standardized requirements found in CSA N288.6-12 Environmental risk assessment at Class I nuclear facilities and uranium mines and mills (CSA 2012).

Public Summary - Environmental Risk Assessment - McArthur River Operation (PDF 6.7 MB)

Public Summary - Environmental Risk Assessment - Key Lake Operation (PDF 3.8 MB)

Tailings Management

Tailings, or what remains of the ore after the uranium has been removed at the Key Lake mill, is placed in the Deilmann tailings management facility. Commissioned in 1996, the facility is built into the mined out Deilmann pit and is designed to safely contain the tailings during continuing operations and after decommissioning. Tailings are placed in the pit under a water cover. During operations, groundwater is collected from a series of wells around the facility and is treated prior to release to the environment. When operations cease, the tailings will become a solid dense mass and groundwater will flow around the tailings, rather than through them, to minimize environmental impact.

Prior to 1996, tailings from the Key Lake mill were deposited in a surface tailings management facility approximately 600 metres by 600 metres and 15 metres deep. The facility was constructed five metres above the groundwater table and used a modified bentonite liner to isolate the tailings from the surrounding soil.

Regulatory Oversight

The primary regulator for the McArthur River and Key Lake operations is the Canadian Nuclear Safety Commission (CNSC). These operations are also subject to regulatory oversight from several other federal and provincial agencies including Saskatchewan Ministry of Environment. Federal and provincial regulators conduct regular site inspections and audits to verify that people and the environment are protected. Uranium mining and milling operations in Canada are licensed by the CNSC.

Sustainability at Cameco

When measuring the sustainability and ethical impact of a company, environmental, social and governance (ESG) are key factors considered by the public and investors. Sustainability and ESG matters have been an important focus at Cameco for many years and we have a strong performance record.

Learn more