Coal Tar FAQ's

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What is Coal Tar?

Coal tar is a black or amber coloured tar-like mixture of many types of petroleum hydrocarbon chemicals. It has a very pungent smell of mothballs due to the presence of naphthalene. Coal tar is usually regarded as a waste but has been beneficially used as a wood preservative, roofing sealant, lubricant and in therapeutic shampoos and creams to treat dandruff, psoriasis and other skin ailments. Some of the chemicals found in coal tar may be hazardous to human health or the environment if they are present in sufficiently high concentrations.

Where did it come from in Kingston?

Before natural gas was available in Eastern North America, coal gas was used extensively to light and heat homes and businesses. Coal gasification plants processed raw coal to produce the gas. A by-product of gas production was coal tar.

Kingston's coal gasification plant operated within a two-block area of the City's downtown from the mid 1800's through to the 1950's. The coal tar produced by the plant was stored within the bottoms of large "gas holders" that had been excavated right into the limestone bedrock. It is not known where all the coal tar produced by the plant ended up. Some may have been sold or used by others for wood preservative, roofing or other uses, and some was left in the bottom of the abandoned gas holders on site.

What is the history of clean up operations?

In 1999 and 2000 the City of Kingston spent over $2 million dollars demolishing buildings and cleaning up coal tar and other contaminants from the site of the former coal gasification works.

Large volumes of contaminated soils and groundwater, as well as pure coal tar, were removed from the properties for proper treatment or disposal. The old gas work properties were cleaned right down to bedrock and then clean soils were placed back on top to create the parking area that we have today.
Because coal tar is mostly heavier than water, much of the coal tar that leaked from the old gas works settled down through the groundwater into the cracks and joints of the limestone bedrock. The coal tar that remains trapped in the limestone cannot be removed. For this reason the City employed a risk management approach to dealing with the left over coal tar.
The risk management approach involved determining what the risk would be if buildings were rebuilt over the cleaned up sites, knowing that coal tar was still present in the deep bedrock. The end result was a Risk Management Plan that allows for site redevelopment provided certain restrictions are adhered to. These restrictions include no below grade or first floor residential occupancy, good ventilation of any underground parking areas and ongoing testing of indoor air quality. In summary - redevelopment and use of this property can occur safely.

Can the deep groundwater be cleaned up?

The short answer is no. Coal tar is a thick, sticky tar material that is stuck in the cracks and joints of the limestone bedrock. It can't be pumped out because of the nature of the fractured bedrock in this area and because of the depth at which the coal tar is found.


How big is the Coal Tar problem?

Since the clean-up of the former coal gasification sites was completed in 2000, the City has been working with the Ministry of the Environment to test the deep bedrock in the downtown to determine how far underground the coal tar was able to migrate.

In some cases, private properties may have coal tar or coal tar compounds in the deep groundwater beneath them. In these cases the City is working with individual property owners to find solutions to their concerns and make sure no one's health is at risk.

Is it safe to live or work in a building that has Coal Tar beneath it?

Yes. There are three principle ways in which people can become exposed to coal tar compounds: by eating or drinking food or water that is contaminated with coal tar compounds (ingestion exposure), by getting coal tar or substances contaminated by coal tar on your skin (dermal exposure), or by breathing in vapours containing coal tar compounds (inhalation exposure). Since coal tar in Kingston's downtown is restricted to the deep bedrock groundwater, and since nobody uses water wells in this area, the only way in which people can be exposed to coal tar is by breathing in volatile coal tar vapours that might rise up and become trapped in indoor building spaces.

The City has found coal tar beneath the Kingston Police Station and beneath the 19-23 Queen Street buildings. As a result, the indoor air quality within these buildings has been extensively tested. The results continue to show that no risk to human health is present due to the coal tar and that the buildings are safe to occupy.
Work done recently by the Province has also detected some coal tar compounds within the deep bedrock groundwater beneath the OHIP building at the corner of Wellington Street and Place D'Armes. The Province conducted extensive testing of the indoor air quality within the OHIP building and found no evidence of coal tar vapours inside.
However, since each building is different (different sizes, types of ventilation systems, depths of basements, etc.), each building that is found to have coal tar beneath it should be assessed in order to assure occupants that there are no coal tar contaminants present in the indoor air.

How do I know if Coal Tar vapours are in my building?

If coal tar or coal tar compounds are not found within the deep bedrock groundwater beneath your building then there is little chance that the volatile coal tar vapours are affecting you.

If your building is found to have coal tar compounds beneath it then the best way to determine if they are causing any affect is for a qualified person to conduct an indoor air quality (IAQ) assessment of your building. An IAQ assessment consists of pumping air through a special filter for several hours. The special filter is designed to trap any chemicals that could be related to coal tar. An air quality technician will set up the sampling filters and once the test is completed they will send the filters to a laboratory to determine if coal tar compounds are present.
An IAQ assessment is a very sensitive process and there are many common household products (perfumes, paints and glues, cleaning agents, tobacco smoke, automobile exhaust) that can interfere with the assessment and cause false readings. The air quality technician will examine the building before running a test to make sure that these interfering factors are not present.
Experienced industrial hygienists review the results of the testing and compare what was found with safe limits published by Federal and Provincial health agencies.

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