The Deloro site cleanup project
Information on the cleanup at the Deloro site in the Municipality of Marmora and Lake.
About the project
The Village of Deloro has a population of 160 and is located 65 kilometres east of Peterborough. The village sits next to a 202-hectare former mine and industrial site. The Moira River runs through the site and flows into the Bay of Quinte on Lake Ontario.
The Deloro site is an abandoned mine and industrial area. Contaminants at the site include:
- low-level radioactive waste and other materials
Work is underway to contain these wastes and other contaminated materials so the area is safe for people and the environment. The project site is divided into three cleanup areas:
- Tailings Area - where over 136,140 cubic metres of waste and byproducts left over from mining and metal production are safely secured.
- Industrial and Mine Area - where approximately 365,865 cubic metres of metal and industrial waste are safely secured.
- Young’s Creek Area - where about 110,000 cubic metres of contaminated sediments will be removed and safely secured.
The cleanup activities include:
- building two large engineered covers (multi-layer barriers that isolate the waste and prevent water from coming into contact with it)
- building one engineered containment cell (a fully lined disposal area with multiple barriers to isolate and secure the waste for long term storage)
- directing rain and melting snow away from the engineered covers to keep water from getting to the contaminated material and spreading it further
- operating an arsenic treatment plant to pump and treat contaminated groundwater
At the end of the project, the site will be a closed and controlled hazardous waste facility. It will not accept waste from outside the site.
How the site was polluted
This site was polluted from the materials mined, refined and produced there. These include:
- gold ore that was combined with naturally occurring arsenic and later refined into pesticides
- metal-containing ores that were processed into silver, arsenic, and cobalt metal
- low-level radioactive material that came from refining-spent ore from Port Hope
The Ontario government took the owner of the Deloro site to court to try to recover costs for dealing with the pollution left behind. However, the company dissolved and Ontario was unable to recover any costs.
Overview of the progress to date
The cleanup project is 75 per cent complete and has already significantly improved the environmental conditions at the site.
Progress highlights include:
- safely securing over 130,000 cubic metres of contaminated tailings materials (the waste and byproducts left over from mining and extracting resources) below an 8.5-hectare engineered cover in the Tailings Area
- isolating over 300,000 cubic metres of contaminated soil and debris from the Industrial and Mine Area and safely containing the waste below a multi-layer engineered cover
- building a water collection system to pump contaminated groundwater to an on-site facility where it is treated for arsenic
- preventing about 42 million litres of contaminated groundwater in the Tailings Area from going into the Moira River between 2012 and 2017
- collecting and treating over 43 million litres of contaminated groundwater from the Industrial and Mine Area in 2017 alone
Young’s Creek Area:
- a pilot project removed and safely secured 12,500 cubic metres of contaminated sediments from part of the Young’s Creek floodplain. The results of the pilot project will help confirm the methods and resources required to complete the remaining cleanup work
Industrial and Mine Area:
- built two storm water management ponds to:
- collect rain water or melted snow flowing through the site
- minimize erosion and reduce the sediments getting into the Moira River during periods of heavy rain or snowfall
- planted 250 native trees (basswood and red maple) and a variety of shrubs and grasses
Young’s Creek Area:
- excavated and safely contained contaminated sediments from part of the floodplain area as part of a pilot project
Industrial and Mine Area:
- built a trench and drain system along the west side of the site to divert clean groundwater away from the contaminated materials
- built a new drying bed for the sludge produced by the arsenic treatment process
- finished excavating the remaining hazardous waste from the industrial area
- built an engineered cover over the most highly contaminated materials on the project site
Young’s Creek Area:
- finished building the base of the containment cell
Industrial and Mine Area:
- finished cleaning up the riverbank
- finished excavating 95 per cent of remaining hazardous waste on the industrial area
- began site restoration work, including planting grasses to return the remediated areas to a more natural state
- continued building a trench and drain system to divert clean water away from the contaminated materials
- consolidated waste material and began work on the engineered cover
- dug out hazardous waste and low-level radioactive material and secured it in the consolidated waste disposal site
- removed contaminated soil from part of the bank of the Moira River
- started constructing a trench and drain system along the west side of the site
Young’s Creek Area:
- began constructing the base layer of a containment cell to hold and secure contaminated sediments
- built a wastewater management pond
- removed contaminated sediment in areas north of Highway 7
- upgraded existing collection systems for groundwater and leachate (water that has passed through a solid and picked up some of its contaminants)
- added a new pumping station to collect and treat arsenic-contaminated water and groundwater from the industrial and mining area
- dug out and consolidated hazardous waste and low-level radioactive material from the mining area
- completed construction of an engineered cover (started in April 2011)
- cleared trees and removed vegetation
- built a clay berm — the “footprint” of an engineered cover
- installed a piping system to collect clean rain water and snowmelt and drain it away
Arsenic treatment plant
The on-site arsenic treatment plant treats arsenic-contaminated groundwater collected from the site. The groundwater collection system includes:
- an 80-metre concrete underground wall to stop groundwater from getting into the Moira River
- a clay-lined contaminated water holding pond
- nine pumping stations
Water is pumped to the treatment plant where the arsenic is removed. The clean water goes to the Moira River.
Before the plant started to operate in 1983, the average annual arsenic concentration in the Moira River was 0.33 milligrams per litre at the site boundary.
In 2017, the average annual arsenic concentration at the same location of the Moira River was about 0.01 milligrams per litre — which means the amount of arsenic going into the Moira River from the Deloro site has been reduced by over 90 per cent.
The treatment plant treated over 68 million litres of contaminated groundwater and removed approximately 1,542 kilograms of arsenic in 2017 alone.
Young’s Creek cleanup
The Young’s Creek floodplain is a provincially significant wetland that starts on the Deloro site and joins the Moira River south of Highway 7.
High levels of arsenic and metals are in the sediment and there is low-level radioactive material on the site only.
The cleanup plan includes:
- excavating and removing contaminated sediment and soil from the floodplain
- securing the contaminated sediments within a large, engineered containment cell built in the area
You should not swim, fish, or drink water from the Young’s Creek off-site area.
The site is highly contaminated with arsenic and metals. Ontario has posted warning signs in the area and notified property owners directly.
Part of the Moira River flows through the Deloro site and ultimately discharges to Lake Ontario at Belleville.
A 1999 study looked at water and sediment quality and the health of fish and other aquatic life.
It found the historical contamination from nearly 100 years of mining and refining at the Deloro site had not greatly affected the aquatic life in a negative way.
You are safe to swim anywhere in the Moira River and in Moira and Stoco Lakes — unless you see a notice posted by the local health unit warning about bacteria levels.
Most fish in the river system are safe to eat.
You can read about the types and amounts of fish that are safe to eat in the Guide to Eating Ontario Fish.
You should not drink or consume water from the river between the Deloro site and Moira Lake or from the lake itself unless you have a treatment system that can remove arsenic, like a reverse osmosis filtration system. Levels of arsenic in this section of the river are higher than the Ontario Drinking Water Quality Standards.
Ontario and the Hastings and Prince Edward Counties Health Unit issue annual reminders to residents along this section of the river.
Deloro Village Environmental Health Risk Study
A detailed environmental health risk study was conducted in 1998-99 in the Village of Deloro.
The study tested thousands of samples and looked at potential health risks. It showed the soil had raised levels of arsenic and metals but did not show any health risks to residents.
If you are interested in reviewing these sampling results, please contact the Ministry of the Environment, Conservation and Parks, Eastern Region Office at
Science and engineering work
There are a number of technical and scientific reports related to on-site and off-site studies, including:
- a full Environmental Assessment Study Report
- technical reports used to develop the cleanup plan
- reports related to archaeological and heritage aspects of the site
Ontario consulted with the public on:
- the cleanup plan
- the environmental assessment
- the Moira River Study
- the cultural heritage evaluation of the site
Public Liaison Committee
The Public Liaison Committee meets twice a year to share information and receive public input on all aspects of the project.
The committee is made up of:
- Village of Deloro residents
- representatives from local municipalities
- local environmental groups
- local property owners’ associations
- interested individuals
Meetings are open and new members are welcome. If you would like to be a member of the Public Liaison Committee, please contact us.
Construction and on-site work information
7 a.m. – 6 p.m.
Contractors can work until 10 p.m., seven days a week according to the municipality’s noise by-law.
Trucks enter through the site’s back entrance from Highway 7. An on-site bridge was upgraded in 2012 to keep heavy truck traffic from going through the Village of Deloro.
Dust control and air monitoring
Dust control measures are in place and will remain so throughout construction. The contractor will use water and other dust suppressants on roads and disturbed soil. Work will be minimized in periods of high winds.
Ontario monitors surface water and groundwater quality at the site.
You can see and bid on construction contracts through the government’s electronic tendering service.
Visit the Ontario Tenders Portal website to subscribe to the service or get more information.
Accessing the site
The site is not open for public tours.
You can access a viewing platform just outside the gates, near the Arsenic Treatment Plant, located east of the Deloro Road and O’Brien Street intersection. You can also view interpretive display panels at this location.
Trespassing will increase your risk of being exposed to high levels of contamination on the site. Hazards from construction and historic mining activities also present safety risks.
Trespassers can be prosecuted and fined.
Report suspicious activity
For immediate concerns about suspicious activity at the site after hours or on weekends, contact: