Developers of two buildings that flank the World Trade Center site are balking at a plan to create a three-story hill in their sight lines, obstructing their views of Ground Zero. The Lower Manhattan Development Corporation voted last week to move vehicle ramps to the south side of Liberty Street, where they will be hidden under the hill at the proposed Liberty Park.

The two buildings, which are in the process of being made habitable, are the only surviving buildings at the World Trade Center site: a 23-floor luxury high-rise at 90 West St., and a 135,000-square-foot structure at 130 Cedar St.

The ramps, which will lead to underground parking and loading docks operated by the Port Authority of New York and New Jersey, have been through a number of iterations. Most recently, the ramps were to be on the north side of Liberty Street, but their position was moved to allow two-way street traffic on Liberty Street and to separate them from the Ground Zero Memorial.

“When we became aware they were moving the ramps, we became very concerned, because it makes the retail on the ground floor of our building less valuable, changing the economics of the development,” an executive familiar with the development at 130 Cedar told The New York Sun.

“We’re trying to work with the Port Authority and the LMDC to see what can be done,” the executive said.

If a compromise cannot be reached, the source said, “We’ll have to talk to our financial backers about other options.”

“Anything that blocks access or visibility to retail severely impacts its value, rendering it pretty much valueless,” a managing director at CB Richard Ellis, Alan Schmerzler, said. “It would be a very tough sale to put retailers in these buildings, even with the foot traffic from the World Trade Center.”

“A visual deterrent is a big loss, particularly if it comes after you already have planned a development,” a commercial broker at Studley, Woody Heller, said.

While developers at 130 Cedar are still at the initial stages of construction, the rental building at 90 West is nearly completed.

“While we are concerned with every aspect of the project plan for Lower Manhattan, this is a city where nearly every building has a 22-story building next to it, so to have a landscaped terrace that is two to three stories high is not the worst thing,” a principal of the Kibel Companies, Peter Levenson, said. Kibel and Brack Capital Real Estate together own 90 West St.

Analysts said that despite the upbeat attitude about that building, with its restoration nearly complete and 410 rentals scheduled to hit the market this spring, it is too late to bemoan the change.

“There isn’t a damn thing they can do about it now,” a senior managing director of Colliers ABR, Craig Evans, said. “I guess they could try and fill the first few floors with office space, but there isn’t much demand for it. I’d be upset if I were them.”

The landmark building, which was built in 1907 by Cass Gilbert, does include retail space on the ground floor, although leases have yet to be made final, the head of on-site marketing, Clifford Finn, said.

“No matter what anyone says, this is so bad, I could almost argue that you could forget even applying any retail value to the lower floors,” Mr. Schmerzler said.

The rentals, which are to be ready for occupancy by mid-April or May, range from $1,595 for a studio to $3,695 for a two-bedroom apartment. Units facing the ramps and construction continuing at Ground Zero will cost less than apartments with river and city views, Mr. Finn said.

The Port Authority said the ramps’ height is predetermined, although a spokesman said the authority hopes a landscape architect will be able to camouflage the height.

“There isn’t a whole lot we can do about the height, it is just the geometry of getting the trucks underground,” a Port Authority spokesman, Steve Coleman, said. “The ramps are going to be about 20 to 25 feet above street level, and it isn’t going to get any lower, although we will cover it with landscaping.”

Officials of the Lower Manhattan Development Corporation are more optimistic than colleagues at the Port Authority that a compromise with concerned developers will be hammered out.

“The Port Authority is not the final word,” the development corporation’s president, Kevin Rampe, said. “The ramp could be made lower. There are different ways to treat these ramps as assets instead of as eyesores.”