TORONTO - Home and business owners across a swath of southern Ontario are accusing Hydro One of riding roughshod over their rights and properties as the transmission utility forges ahead with plans to build a 180-kilometre high-tension power line.

It's an issue that seems destined to reappear in the future as environmentally friendly windfarms are built and power lines put up to move the power to market.

Almost 350 landowners are affected by the proposed $635-million line that is to be strung on 700 pylons from the shores of Lake Huron to Milton, Ont., west of Toronto, and put in service by Dec. 1, 2011.

The current project, which will expand an existing hydro corridor carrying two lines, will force about 30 families from their properties altogether.

The remainder worry about the impact pylons and cables have on the value of their property.

Dennis Threndyle, whose family farm is located in Bruce County outside Elmwood, said Hydro One is offering about $60,000 less than what the family believes it should get for having a line stung across the top of the property.

"They're low-balling us," said Threndyle, who insists he understands the need for the project.

When they wanted to negotiate, he said, Hydro One's reaction was "accept or decline," he said.

The utility has estimated property-value losses at between three per cent for a vacant agricultural property and 20 per cent in cases where the line will run close to a home.

Gary Schneider, Hydro One's project director, said valuations were based on an assessment of five representative properties by two appraisers -- one for the utility and one for the landowners.

Owners can possibly get more compensation if they get a second appraisal to back that up, or have an arbitrator choose which of the competing valuations to accept, Schneider said.

Only 25 owners have signed onto Hydro One's offer, but about 75 others have asked for draft legal agreements on a voluntary settlement.

"That to me is a great sign," Schneider said.

Hydro One is offering property owners a $4,000 signing bonus -- if they don't opt for their own independent appraisal.

"It's like negotiating with a gun to your head," said Ben Lansink, a real estate appraiser and consultant based in London, Ont.

Lansink, who is acting for about 50 landowners, advised against signing anything until he completes his own study in a few months because valuations he's seen appear to be "on the low side."

Some homeowners, such as Pat Crouse, were initially told they would have to move out but learned more than a year later the proposed route had changed.

In the interim, their property and business values plunged but Hydro One argues they have no right to compensation.

"We have a condemned piece of property that we cannot sell unless we give it away," said Crouse, 58, whose retirement dreams have been devastated by an estimated $180,000 hit on the value of their home.

"We are basically screwed."

Rob Barlow, a businessman in Limehouse, Ont., said Hydro One had cost him his computer dealership even though it now appears the line will not cross his property as initially planned.

"The stress they put on your family is awful," he said.

Schneider said he expected final environmental approvals within a few months and said the utility would move to expropriate a month later.

If owners opt to go through the expropriation process -- often a lengthy and costly legal battle -- it would impact the construction schedule, he said.

A lawyer from Durham, Ont., wrote Environment Minister John Gerretsen this month to complain his ministry had failed to notify affected owners it was seeking final public input into the project.

A Gerretsen spokesman said a response was being prepared.