Stanford University's plans to build new academic buildings and houses on its campus received a major boost Tuesday afternoon: The Santa Clara County Board of Supervisors approved a study detailing Stanford's land-use vision over the next 25 years.

But board members also indicated that Stanford would probably be asked to provide more details --including performance measures for its efforts on sustainability and mitigating its impacts on neighboring community -- when it comes back to the board for its next major build-out permit.

The board voted 3-2, with Supervisors Donald Gage and George Shirakawa dissenting, to approve the Stanford Sustainable Development Study along with a list of recommendations proposed by board President Liz Kniss. The approval came only after Stanford officials assured the supervisors that the university would not need to expand its developments into the foothills in any foreseeable future.

"This allows Stanford to move forward and it also allows us to be the same good stewards of this unincorporated, very large piece of property in the northern part of the county," Kniss said.

Gage and Shirakawa also backed the detailed, map-heavy study, but both said they weren't comfortable with Kniss' list of recommendations.

The list included asking Stanford to provide a similar study around the halfway point of its next general use permit; recommending that Stanford's next study include mitigations to reduce impacts on neighboring communities; requiring Stanford to project the square footage of its future housing developments; and requesting that the next study include performance measures for the university's efforts to promote conservation and energy efficiency.

Supervisors Ken Yeager and Dave Cortese sided with Kniss.

But even with these conditions, Kniss said the deal between the county and Stanford is a "compromise."

Kniss, a former Palo Alto mayor, expressed the same concern the Palo Alto City Council voiced when it scrutinized the study in February: The 2035 planning horizon, she said, doesn't stretch far enough.

When the county approved Stanford's general use permit in 2000, allowing up to 2 million square feet of development, it asked the university to perform a study before it completes developing the first 1 million square feet. The board asked Stanford to consider its "maximum planned build-out potential" and did not specify any particular time horizon.

Palo Alto and other jurisdictions argued over the past two months that the 2035 time horizon in Stanford's study fails to comply with the 2000 directive.

But Stanford officials argued that extending the study further would accomplish very little besides forcing the school to make wild guesses. Stanford Provost John Etchemendy urged the board to approve the study and emphasized that any longer-term planning would be based on little more than conjecture.

"It's a wild, wild guess where we will be in 2035 and 2050," Etchemendy said. "Based on my knowledge of where we're headed, I can probably give you a pretty good idea of where we'll be in 10 years, based on substance.

"Beyond that 10 years, in the next 15 years, it's just guesswork."

The county's planning staff sided with Stanford and wrote in its report that the 25-year time frame is comparable to other long-range planning documents.

"The terminology used within the Community Plan policy, 'maximum planned build-out potential' is vague," the report stated. "Forecasting beyond the 25-year timeframe becomes less reliable, difficult to validate, and becomes more difficult to anticipate the University's needs as technology, academic programs and the structure of providing higher education change."

But Brian Schmidt, legislative advocate for the Committee for Green Foothills, rejected county staff's and Stanford's logic. The supervisors intended in 2000 to request a study addressing a maximum build-out, not a 25-year build-out, he noted. Stanford should be asked to provide a development vision going at least as far as 2050, if not further, he said.

Kniss and Palo Alto officials also argued in favor of the 2050 horizon.

"The current study should be rejected until it extends closer to what Stanford committed to," Schmidt told the board.

The study lays out three growth scenarios for Stanford. Under the moderate-growth scenario, which university officials said is the most likely one, the university would build 3.5 million square feet of space by 2035. Under the minimal-growth and aggressive-growth scenarios, the school would grow by 2 million and 5 million square feet, respectively.

The study doesn't consider the Stanford University Medical Center, the Stanford Shopping Center, or any other Stanford properties within Palo Alto's jurisdiction. It focuses on the campus, which is on county land, and identifies several new academic facilities the university hopes to add, including a new "Arts District" and a new Graduate School of Business. Stanford is also in the midst of constructing a new Science and Engineering Quad.

Gage and Shirakawa both said they were pleased with the study and offered no objections to any of its contents. But Gage said he would not support Kniss' proposal because he hadn't had time to carefully consider her list of recommendations.

"I haven't had an opportunity to think this through," Gage told Kniss. "I appreciate the hard work you're doing, but I don't feel comfortable in going beyond what this (report) is asking us to do."