As it became obvious in recent months that Yale’s two new residential colleges would be delayed, University officials still managed to sound a hopeful note.

Even if construction could not start on time in 2011, they said at the time, designs and drawings for the project would be complete by late 2010 and workers could have shovels in the ground as soon as the economy improved. All Yale needed to do in the meantime was pay its architects. But that, it turns out, is easier said than done.

While the University has received $154.7 million in pledges for the new colleges, Vice President for Development Inge Reichenbach said not all of that money will go to the design and construction of the buildings themselves. Donors can choose to give either for the bricks and mortar or for the other parts of the expansion project, such as the new professorships and expanded financial aid that will be required to sustain a larger Yale.

So far, Reichenbach said, most donors — including one person who pledged a “very large gift” — have not decided where they want their money to go.

If designs are to be completed as soon as possible, though, Yale will need at least a few major donors to step up now and allocate funds for the planning and construction.

“We’re trying to explore ways to continue the design work,” University President Richard Levin said. “We need to raise more money to go to the next stage.”

According to Yale’s Capital Projects Handbook, there are two primary stages of design for each major building project. During the planning phase for a new building, feasibility and programming studies are conducted to decide upon the scope of the project — such as how many dorm rooms to build — and the approximate cost of construction. Levin said Robert A.M. Stern Architects, the New York-based firm that is designing the new colleges, has already completed this work.

The architects have moved onto the second phase, called preliminary design. Over the next several months, the designers will continue to refine their plans, taking into account code requirements and fleshing out the specifics of everything — from entryway locations to dorm room layouts. Yale has raised enough money, Levin said, to finish this preliminary design phase.

By summer, though, the architects will be done with this stage and ready to move on to design development. Yale, Levin and Reichenbach said, does not currently have the funds on hand to pay for this work.

During design development, final decisions will be made about the layout and size and appearance of the buildings. According to the guidelines from Yale’s Office of Facilities, design development is the “last opportunity for input regarding design issues.” (After design development comes a construction documents phase, when architects and consultants complete detailed drawings and instructions for builders.)

Given the importance of design development, Levin said he is hopeful that Yale will not have to delay any work on the project. The University still hopes to have drawings ready for construction to start when the economy improves.

Designing buildings is expensive, though, because planning requires the work of not only architects but also landscape architects and structural engineers and other consultants — all of whom must be paid.

Yale’s fundraisers may be aided in their efforts by renderings of the colleges, which are expected to be released sometime after spring break. Those drawings will give donors a better picture of what the buildings will look like when finished, and Reichenbach said she is hopeful that giving to the project will increase as a result.

The names of the colleges themselves remain off the table for donors, Levin said, but generous graduates will be recognized through the naming of courtyards and dining halls and even towers within the complex. There is reason to think, given these opportunities for recognition, that securing the funds needed to continue the design work will not be a large problem.

But nobody is certain.

When asked on Wednesday if design work for the project remained on track, School of Architecture Dean Robert A.M. Stern ARC ’65, who is in charge of the design team for the project, had only this to say: “Yes it is. I think it is.”