May 30, 2008 - 01:35 PM

By Jillian Follert

OSHAWA -- Sarah Ross likes to walk her dog near Harmony Valley Park, but lately the Oshawa resident has been more cautious, after noticing an unusual rust-coloured substance staining the ground.

The liquid is oozing from the side of a seemingly inconspicuous hill, which is actually a decommissioned landfill site.

"I'm really concerned about what it is and whether any monitoring is going on," said Ms. Ross, a master's student in environmental studies. "A lot of people probably don't even realize there's a landfill there because it just looks like a hill. They're walking their dogs in the area and they should know whether there are any risks."

Brent Frew, who recently moved into the nearby neighbourhood, is also concerned.

"It looks like orange goo; it's kind of disgusting," he said. "It's the kind of thing that makes you wonder if it's OK for you to walk around there with your kids."

The landfill sits near the corner of Harmony Road North and Rossland Road East, with Harmony Valley Park on one side and a large residential subdivision on the other.

The site was formerly owned by Industrial Disposal Oshawa Limited (IDOL), and operated as a landfill from 1957 to 1980, when it was sealed.

When it was operational, the 35-acre landfill accepted solid commercial and industrial waste, primarily from General Motors.

The site is now owned by an unknown private operator.

Over the years, the landfill's presence has raised concerns.

Coscan Development Corporation -- which owned three pieces of land near the landfill -- asked the City in the 1990s for a zoning amendment to build a commercial strip and two residential developments near the site.

The City refused, saying the landfill posed too large an environmental threat to allow residential development so close by.

The decision was appealed to the Ontario Municipal Board (OMB), which eventually sided with the developer after hearing from a slew of expert witnesses.

In its 1995 decision, the OMB notes IDOL made it difficult to assess the environmental risks because it refused access to the land. However, it also indicates that over the years, IDOL had followed all orders from the Ministry of the Environment (MOE) such as the installation of a subsurface leachate collection system and the placement of a two-foot-thick cover over the site.

Leachate is a quantity of liquid that has worked through a solid and leached out some of its substance.

In its ruling, the board calls the concerns expressed by the City and its consultants "cautious in the extreme," and said development should be allowed as long as certain precautions were taken.

Those included:

- requiring the developer to perform monitoring for leachate presence and migration every five years starting in 2000;

- a two-metre high fence around the landfill site to keep pedestrians out;

- requiring the developer to give the City a $30,000 letter of credit to be used in the event it didn't comply with the monitoring or remedial work ordered by the MOE.

Phil Dunn, a MOE senior environmental officer, said the ministry inspects the site periodically and the developer and private owner continue to conduct their own monitoring.

Mr. Dunn said there are no concerns at this time and that the mysterious rust-coloured liquid spotted by residents is "iron staining," which is not uncommon in older landfills.

As precipitation in the form of rain and snow percolates through the landfill matter, it picks up matter from the waste inside and carries it outside. This is called leachate and when it oxidizes and dries, the iron component can leave an orange stain.

Mr. Dunn stressed it is not cause for concern.

"We have monitoring information that indicates the impact to the ground and surface water is very minimal," he said. "And it wouldn't pose any risk to anyone walking on the site."

Mostafa Warith, a professor in the civil engineering department at Ryerson University, has spent the past 25 years studying landfills around the world.

He said it is impossible to prevent leachate from occurring at a landfill because there will always be rain, snow, groundwater and liquid in the waste itself.

The level of risk depends entirely on the contents of the leachate, which can range from organics to heavy metals depending on they type of waste in the landfill, he said.

"Leachate is a contaminated liquid," he said. "If it gets out, it will end up somewhere -- in the groundwater, in the creeks and streams. That's why proper monitoring is needed."

The professor couldn't comment on the north Oshawa site specifically but said if iron staining is occurring in large amounts, it could indicate leachate is not being properly collected or redirected.

He said there are many new engineering tools available to ensure leachate doesn't pose an environmental threat but said in a private site like this, it would be up to the operator to pursue those unless MOE issued an order.

Ward 6 Regional Councillor April Cullen is familiar with the site and sent flyers to homeowners in the nearby subdivision years ago to let them know there are no known environmental concerns.

"I was actually looking into buying a house in that subdivision at one point and I would never have done that if I thought there was anything to worry about," she said. "If there was any concern at all, we would be notified and I would make sure we took action."

Coun. Cullen said that while the site isn't dangerous, it also isn't intended for people to walk their dogs or take their kids for a stroll -- that's what the adjacent Harmony Valley Park is for.

Residents who are new to the city or the neighbourhood might not know that it's a landfill, especially because the fencing around it is constantly being ripped down, she said.