The proposed expansion of Adventist Health Castle, formerly Castle Medical Center, at Hawaii Pacific University’s Hawaii Loa campus is projected to cost $438 million, according to a draft environmental impact statement.

Adventist is planning to turn HPU’s sprawling Windward location into a medical campus with a cancer center, outpatient services and physician office buildings surrounding a new 160-bed hospital.

The draft, filed Feb. 12 by architectural and design firm G70 with the state Department of Health, lays out a 15-year master plan for the 132 acres of land Adventist purchased in 2016 from the university to expand its medical campus at 45-045 Kamehameha Highway. The deal allows the college to consolidate its campus downtown and the hospital to expand its health care offerings.

The first phase, initially projected to break ground next year, is not expected to start for five years, said Adventist President Kathryn Raethal.

“HPU is going to lease back the property. They’re not moving as quickly on their downtown expansion, and so they’re going to continue leasing that from us for the next two to three years. This is a very long-range plan for us at Castle,” she said. “Things are just moving more slowly than we had thought back then.”

The first phase, which includes converting the existing HPU academic center into a cancer center, with a 5,000-square-foot radiation treatment area, and adding parking for 125 cars, is projected to cost $37 million.

The second part of the project — two four-story buildings, to be built on the current soccer field, for ambulatory and outpatient services — is estimated at $106 million. That phase includes a 19,000-square-foot building for primary care and wellness services, imaging and outpatient surgical and minor procedures. A cafe and retail shop are also proposed for the ambulatory building.

A new 160-bed, four-story hospital measuring 92,650 square feet is part of the final phase, projected to cost $295 million. That includes adding a second entry and exit point along Kamehameha Highway north of the existing entry for emergency vehicles.

Castle hospital, which first opened in 1963, serves more than 130,000 area residents with 160 beds. It has more than 1,000 employees and more than 300 medical staff. The facility was originally built to meet a critical need for medical care in the region, where residents dealt with part-time ambulance service and unpredictable travel times to Honolulu hospitals.

“We’re excited about it, and we think it’s going to be a wonderful health care campus for Windward Oahu in the future,” Raethal said.