The Arlington County Board has unanimously approved a use permit for a new Washington-Lee High School, clearing the way for a School Board vote tonight on the final design, which was once declared too tall for the site.

The move came Tuesday after years of planning and months of anxiety over rising costs for a project that has outgrown estimates by 15 percent even before being put out for bid. The estimated cost is now more than $95 million, with the figure rising about $500,000 each month construction is delayed.

Before approving the permit, the board had to address a zoning problem caused by what county and school officials called a miscommunication.

School officials said they knew their plan for a four-story, 63-foot-tall school violated the 45-foot height limit for the area but believed that county officials had told them it could be waived. Last month, county officials said the problem was more complicated and would require a zoning amendment.

After the Planning Commission recommended its approval, the County Board passed a zoning amendment Tuesday to allow exceptions to the height regulation for high schools and school administration buildings on sites of 19 acres or larger. That applies to only two buildings: Washington-Lee, on 19 acres, and Wakefield High School, on 40 acres.

After the permit vote, board Chairman Jay Fisette (D) joked, "And that is the end of the discussion of Washington-Lee High School for this century."

But Vice Chairman Chris Zimmerman (D) called the vote a "forced" choice between delaying a much-needed school or settling for an imperfect design. He said the building should be closer to the major intersection at Washington Boulevard and North Quincy Street, away from single-story homes.

Zimmerman said the planning and transportation commissions should have been brought into the decision making earlier instead of "looking at it effectively at the end of the process when it's too late to change it."

Sarah Woodhead, director of design and construction for Arlington schools, said the schedule for involvement of the commissions was "not as effective as some would have liked, so the two boards are going to . . . look at improving the process."

Construction on Washington-Lee, originally scheduled to start this month, is on track to begin in January at the earliest. The original project estimate was $82 million, and a bond approved by voters in November was to have covered most of that cost. The School Board will hold a work session next Thursday to discuss how to meet the rising costs of the project.

Rising prices have dogged school construction projects throughout the county, including renovation plans for Nottingham Elementary School and H-B Woodlawn Secondary Program. Other renovation projects are in the pipeline, but school officials said the 81-year-old Washington-Lee, which has had so many parts removed and added over the years that the original building no longer exists, is highest on their list.

The new building will be 350,000 square feet, up from the current 225,000 square feet, while retaining the school's 1,600-student capacity. With its taller design, its footprint on the site will be smaller, freeing an additional acre of outdoor space.

Expected to be completed in 2009, it will be the one of the first schools in the nation to apply for a Leadership in Energy and Environmental Design certification, awarded by the U.S. Green Building Council.

To qualify, contractors will use construction materials from nearby producers and recycle construction debris. The design's environmentally beneficial elements will include a reflective roof; a partially "green" roof planted with vegetation; and a lot of natural light, which studies show enhances student performance.

One other Arlington school, the John M. Langston High School Continuation Program, has the environmental design certification, and T.C. Williams High School in Alexandria, which is undergoing a similar reconstruction, also plans to apply.

The proposed redesign for Washington-Lee High School, currently estimated to cost $95 million, would make the environmentally sensitive facility four stories high, almost 20 feet taller than zoning allowed.