The recession has sent the projects of many developers in a tailspin, but Michael D’Ambra is moving ahead with the design of a $250 million to $300 million office and hotel development that coupled with the airport Intermodal project will transform the city’s skyline.

“Right now the risk is in the design,” D’Ambra said yesterday from the offices of his construction company on Jefferson Boulevard. If all goes according to D’Ambra’s plans, the existing office building will become the site of a full service 320-room hotel and the adjoining asphalt plant, which D’Ambra also owns and operates, will be the site for three 7-story office towers with a total of 540,000 square feet.

D’Ambra estimates he will have sunk $500,000 in designs for the project.

“But the big risk,” he said, “is when you put a shovel in the ground.” D’Ambra said he wouldn’t take that step until at least 50 percent of the first office building is leased.

And how long might that be?

D’Ambra is hopeful the economy will turn the corner in the third or fourth quarter of 2010 and with development of the $266 million Intermodal projected slated for completion by next September there will be a demand for “Class A” office space at better rates offered by metropolitan areas.

“We’ll have a better product for less money than Boston, New York or Providence with the amenity of the train right here,” he said. Presently office rental rates are in the mid $30 per square foot in Providence and about $10 cheaper in the suburbs. He hasn’t finalized office rates for the project, but evidently they will fall somewhere between those two numbers.

D’Ambra sees corporations with offices in the suburbs as well as companies from outside the state that want the convenience of MBTA service to Boston from the Intermodal facility and air transportation service at Green Airport as his customer base. D’Ambra has already negotiated an agreement with the Rhode Island Airport Corporation for a connection between the hotel and the skywalk linking the airport terminal and the rental car and commuter-parking garage on Jefferson Boulevard.

D’Ambra said this would enable people to get from the airport to the hotel without going outside. As for the hotel, which would be the second phase of a four-phase construction project, D’Ambra talks about a facility designed to serve business clients with conference accommodations but not the scale of what the Crowne Plaza currently offers.

Plans for the 8.5 acre rectangular lot has the office towers facing Jefferson Boulevard. They would be separated from a parking 2,000-car garage facing Amtrak rail lines by an internal boulevard with access from a signaled intersection at the north end of the project and the hotel.

The massive project has already gained city master plan and zoning approval. D’Ambra is scheduled to appear before the Planning Board Nov. 18 at 6 p.m. in the lower level conference room in City Hall for preliminary plan approval. Assuming that approval is forthcoming, D’Ambra said the design plans should be at a point shortly where he could move ahead with building permit requests.

As a first step to the development, D’Ambra has bought 15-acres from Rhode Island Resource Recovery in Johnston for the relocation of the asphalt processing plant. He said that permitting from the Department of Environmental Management and the Army Corps of Engineers has delayed relocation of the plant. His plan now is to have the plant relocated by late 2010 or early 2011. He commended the cooperation of Johnston town officials in securing the required permitting for the plant.

The overall development project is somewhat of a family affair. All three of D’Ambra’s sons, Michael, Robert and David, work for the company. Michael and Robert are full time employees and David who is at URI studying civil engineering is a part time employee.

D’Ambra’s project and those developed and on the drawing boards of developer Joseph Piscopio promise to dramatically alter the character of Jefferson Boulevard. Piscopio built the Hilton Garden Inn at the boulevard’s Kilvert Street intersection and has plans for a second hotel as well as a residential complex.

Also in the wings is the potential development of the Leviton property of more than 80 acres. Leviton has creased manufacturing at its plant and is presently leasing space at the property.

Mayor Scott Avedisian said this week he has heard of a major development planned for the site, but as of this time no proposals have been submitted for city consideration.