ASPEN — Redevelopment of the Aspen Music School campus on Castle Creek received all but final approval from the Pitkin County commissioners on Wednesday.

The school probably will have to relocate or eliminate one-third of its practice rooms because the school’s campus redevelopment plans had the rooms being built in the path of potential rockslides, snowslides and other geologic hazards.

And Pitkin County has asked the school to deal with property owners holding old mining claims and tailings piles in the gulch above to school, to determine just how hazardous those century-old leftovers might be.

But beyond those and other mitigation issues, the redevelopment plans won at least part of the approvals needed to rebuild the old campus for the music school and its tenant, the Aspen Country Day School.

Not approved, but scheduled for another meeting on May 14, was the general master plan for the project. The commissioners and officials of the two schools hashed out most of the details contained in the plan, but a formal document granting approval was not prepared for this week’s meeting.

The $70 million project includes tearing down all but three of the existing buildings on the 23-acre campus and building three new music rehearsal halls, a 16,000-square-foot administration and cafeteria building, practice rooms, parking lots and a playing field.

In all, the campus will grow from 50,000 square feet of buildings to 106,000 square feet, in a project being designed by noted local architect Harry Teague.

At the end of more than four hours of discussion on Wednesday, and a total of a dozen meetings over the past year, the Pitkin County commissioners gave initial approvals to ordinances that will permit the school to build “geologic hazard defense structures” on the steep slopes above the school campus, and exceed the county’s normal 28-foot building height with buildings that will reach up to 40 feet high.

The commissioners also agreed to rezone the schools from agricultural uses to the public/institutional zoning category, and placed two of the campus buildings on the county’s historic registry. The buildings are believed to have been the homes of the owner and mine superintendent of the Newman Mine on Aspen Mountain.

A key haggling point in Wednesday’s discussions was the issue of affordable housing.

According to county documents, Aspen County Day School officials have agreed to pay the county $615,000 in “mitigation” for 18 employees expected to be added over the next decade or so. But the music school is adding neither employees nor students, according to officials, and so is not formally required to provide housing mitigation.

But Commissioner Rachel Richards called on music school officials to give “a larger commitment” to helping ease the local affordable housing crunch than strictly the Aspen Country Day School agreement, in light of the height variances and other considerations being granted by the county.

“We’re being asked to make a lot of compromises,” Richards said, adding that both the city of Aspen and Pitkin County have gone to great lengths over the years to support the Music Associates of Aspen (MAA), the parent corporation of the Aspen Music School and Festival.

“We’re just asking you to step forward and solve part of the problem,” added Commissioner Michael Owsley.

Commissioner Dorothea Farris, however, said it would be “putting a burden that we don’t put on other educational institutions” if the county tried to force the MAA to go beyond its stated intention to do what it can to house employees, artists, teachers and students.

Planner Alan Richman, speaking for the applicants, told the board: “The institutions need to create housing, and we understand that.”

Another unresolved issue is the contributions by the MAA and Aspen Country Day School to the $2.2 million-plus cost of building a trail from the Country Day campus to the Marolt Housing complex, along Castle Creek Road. The project stalled last year after a group of neighbors sued, alleging the city of Aspen failed to follow its own land-use rules when planning the project.

The county suggested the schools come up with $800,000 to help pay for the trail, which some say would mostly serve the campus and its student body in the summers. Music Festival and School President Alan Fletcher agreed to talk with his board of directors about contributing to the project.

jcolson@aspentimes.com