Sharon Joyce and her neighbors sit on their decks in Waterway South in West Ashley and watch birds fly across the marsh.

A few times a week, huge flocks of beautiful white ibises grace the horizon. “It looks like snow,” Joyce said.

When she bought her condominium in 2003, nobody was talking about the extension of Interstate 526, she said.

And she had no idea the plan would include a bridge from West Ashley to Johns Island that would cut across the marsh in front of her home.

The road will not only change the view, Joyce said, it will bring noise and pollution.

And it likely will mean a huge loss in the value of her condo, and make it difficult to sell.

The Coastal Conservation League, a group opposed to the completion of I-526 — also known as the Mark Clark Expressway — across Johns and James islands, had a lot of calls from property owners who live within 1,000 feet of the extension, said project manager Jake Libaire.

The residents were concerned about the value of their property after Charleston County Council voted in December to build it. So the group hired the Seattle-based Greenfield Advisors to evaluate the impact of the road on the value of those properties and produce a report.

Greenfield Advisors does economic analyses, with a focus on complex real estate issues, such as litigation, development and preservation.

The news for the homeowners wasn't good. According to the report, nearly 70 percent of about 500 people surveyed said they were unlikely to purchase a home that close to a major road. And more than 60 percent said they thought homes that close to the road should be sold for a discounted price.

The results don't come as a surprise to Joyce. “It limits the size of the market,” she said of the highway's impact on the likelihood of her selling her home. “People are going to think twice before putting their savings into something that close to a major road.”

Joe Hodapp, president of Waterway South Owners Association, said the market will be further limited because the Federal Housing Administration won't back mortgages on condominiums within 1,000 feet of a highway. That restriction will knock out many potential buyers, he said.

Charleston County staffers also are studying the impact of the road on nearby homeowners. When council approved the road, it agreed to put forth “a good faith effort” to compensate people who live near its path for a drop in the value of their property.

Assistant Administrator Jim Armstrong said staffers are studying the issue, and will make a presentation on it to council when they are done. But, he added, they haven't yet decided on the exact path of the road. They can't complete the compensation study until that is done.

“We've never done anything like this before,” Armstrong said. The process is complicated, and it's going to take some time.

Some residents of Waterway South doubt they will ever receive compensation.

“We're not holding our breath,” said Tom Palmer.

Hodapp said he thinks council agreed to consider the compensation proposal to secure the vote of Councilwoman Anna Johnson. The vote to build the road was 5-4.

“I don't think they had any intention of following through with that because they can't,” Hodapp said. The county simply doesn't have the money.

Joyce agrees. And she thinks the Greenfield Advisors report is right on target. “It confirmed what I already know.”

Reach Diane Knich at 937-5491 or on Twitter @dianeknich.