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Independent Environmental Monitoring Program: Deloro closed mine site

The Ontario Ministry of the Environment, Conservation and Parks (MECP) is licensed by the Canadian Nuclear Safety Commission (CNSC) to conduct remediation activities associated with the Young’s Creek Area (YCA) located at the Deloro closed mine site (Deloro site). The Deloro site is an abandoned mine and industrial area located approximately 65 km east of Peterborough, Ontario, adjacent to the former village of Deloro along the banks of the Moira River. The Moira River runs through the Deloro site and flows into Lake Ontario.

The Deloro site began operation as an underground gold mine in the 1860s, and the historical mining, refining, and manufacturing operation closed in 1961. The mining and industrial operations resulted in large volumes of by-products that were deposited on the Deloro site as waste. This waste legacy includes soil, sediment, groundwater and surface water that are contaminated with arsenic, cobalt, copper, nickel and small quantities of low-level radioactive waste. Arsenic is the main contaminant of concern at the Deloro site. Low-level radioactive waste materials containing uranium and its decay products, from historic refining operations in Port Hope, constitute up to 6% of the waste, and coexist with the non-radioactive hazardous wastes. Due to this legacy waste and the ongoing remediation work, public access to the site is prohibited.

The MECP assumed responsibility for the site and the required environmental cleanup when the previous owners abandoned the site. Since 1985, the site has been under the care and control of the MECP, which has implemented measures to control the site’s environmental contamination. These measures include a comprehensive environmental protection program and an ongoing environmental monitoring program. The MECP’s overall cleanup objective for the Deloro site is to achieve a 90% reduction in arsenic discharge to the Moira River, from historical levels, and to ensure appropriate long-term management of the small quantities of low-level radioactive waste.  To meet this cleanup objective, the MECP constructed an arsenic water treatment plant to collect and treat arsenic-contaminated groundwater from the mine site. The arsenic-contaminated water is pumped to the arsenic treatment plant where the arsenic is removed and the treated effluent water is released to the Moira River, under MECP approval. The MECP also constructed two large engineered covers to isolate contaminated materials and an engineered containment cell to securely contain contaminated sediment and waste from the YCA.

The Independent Environmental Monitoring Program (IEMP) results for 2016 and 2018 are consistent with the results from the MECP and indicate that, because of the measures being taken by the MECP, the health and safety of the people and the environment are protected.


Deloro closed mine site


Results Table

1 The < symbol indicates that a result is below the provided laboratory analytical detection limit.

2 N/A – not available


Under the Nuclear Safety and Control Act (NSCA), licensees of nuclear facilities are required to implement an environmental monitoring program to demonstrate that the public and the environment are protected from emissions related to their facilities’ nuclear activities. The results of these monitoring programs are submitted to the CNSC to ensure compliance with applicable guidelines and limits, as set out in the regulations that oversee Canada's nuclear industry.

The CNSC has implemented its IEMP to verify that the public and the environment around licensed nuclear facilities are protected. It is separate from, but complementary to, the CNSC's ongoing compliance verification program. The IEMP involves taking samples from publicly accessible areas around facilities, and measuring and analyzing the amount of radioactive and hazardous substances in those samples. CNSC staff collect the samples and send them to the CNSC's independent laboratory for testing and analysis. Since the IEMP’s implementation, the area outside of the Deloro site perimeter has been sampled twice: once in 2016 and once in 2018.

2016 and 2018 results

The 2016 and 2018 IEMP sampling plan for the Deloro site focused on both radioactive and hazardous contaminants. A site-specific sampling plan was developed based on the MECP's environmental monitoring program and the CNSC’s regulatory experience with the site. In 2016 and 2018, CNSC staff collected sediment and water samples in publicly accessible areas outside the site perimeter, taking into account the known dispersion pathways. This included sampling locations along Young's Creek offsite and the Moira River downstream from the site.

The results of the radioactive analysis in sediment and water samples were below available guidelines and CNSC screening levels. CNSC screening levels are based on conservative assumptions about the exposure that would result in a dose of 0.1 mSv/year. No health impacts are expected at this dose level.

The results of the hazardous analysis showed elevated concentrations of copper and arsenic in some surface water samples and elevated concentrations of nickel, copper, and arsenic in some sediment samples. These water and sediment samples exceed CCME guidelines; however, these heavy metals are contaminants from historical industrial processes at the Deloro site. The concentrations of arsenic in water and sediments of the Moira River system near the Deloro site also exceed CCME guidelines. For some parameters, such as aluminum, cobalt and total organic carbon in sediment, there are no guidelines or CNSC screening values available. The results are consistent and within the range of the MECP’s results and the environmental assessment (EA) conducted as part of the CNSC licensing process for this provincial remediation project. Arsenic at the Deloro site has been significantly reduced further as a result of remediation activities performed by the licensee. Additional planned remediation activities are expected to further reduce arsenic concentrations; however, as the arsenic concentrations are elevated, there is a water consumption advisory downstream of the Deloro site. View detailed sampling data.


The MECP has committed to the ongoing remediation and long-term monitoring and maintenance of the Deloro site. Remediation activities put in place by the MECP have and will continue to ensure that this historic contamination is controlled and managed and that the public is protected. The IEMP results are consistent with those submitted by the MECP, demonstrating that the licensee's environmental protection program protects the health and safety of people and the environment.

To obtain the full technical IEMP reports, contact us at or call 613-995-5894 or 1-800-668-5284 (in Canada). Please provide the name of the facility and the report year.

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