Hawaii’s largest health care provider plans to dramatically enhance services for Leeward Oahu residents in a planned $500 million expansion of The Queen’s Medical Center-West Oahu.

The Queen’s Health Systems is proposing to quadruple the size of its facilities on the 25-acre campus over 15 years to address existing overcapacity issues and accommodate the anticipated future needs of the region’s growing population.

The plan includes building two new hospital towers with patient rooms, expanding an already overtaxed emergency department, developing two new physician’s office buildings with outpatient services, adding a second parking garage and creating two large lawn areas while removing existing surface parking to make the campus greener.

Overall, the number of patient beds would grow to 364 from 104, and total building space would rise to 1 million square feet from 250,000 square feet on the campus bordering West Loch Golf Course between the edges of Waipahu and Ewa Beach.

More than 500 jobs would be created, according to Queen’s.

Jason Chang, the nonprofit organization’s chief operating officer, said the community hospital needs to keep up with community growth.

“We are very full,” he said.

Chang said hospital bed use at Queen’s West Oahu is at 97%, while the emergency department is the second-­most-visited in the state, after The Queen’s Medical Center in Honolulu, and can’t currently handle the demand.

Queen’s is seeking permission for the expansion under a plan review use permit application filed this month with the city Department of Planning and Permitting.

City Council approval following a public hearing is necessary for Queen’s to carry out its plan.

PRU permits serve as a form of zoning regulation under the city’s Land Use Ordinance. Certain types of land uses — hospitals, universities, airports and prisons — can be developed on property zoned for any use with PRU approval.

The Queen’s campus is on land zoned for agriculture in an area once farmed in sugarcane but now largely surrounded by urban uses.

Initial approval for a hospital on the site was given in 1985 for the creation of St. Francis Medical Center-West, which early on included a hospital, a physician’s office building and a medical office building.

Over the next three decades, various additions were approved and constructed, including a kidney dialysis center, a family practice building, a hospice facility and more parking.

However, other expansion and renovation plans by St. Francis weren’t realized, and the organization sold the medical center in 2007 to a partnership involving local doctors and a mainland hospital firm. These new operators filed for bankruptcy in 2008 and then closed the renamed Hawaii Medical Center West in 2011 after a second bout of bankruptcy.

The shutdown strained Oahu’s emergency medical services, as ambulance trips became longer in many instances and overloaded other emergency rooms, while West Oahu residents were left with Pali Momi Medical Center in Aiea as the closest acute-care hospital for medical needs.

Queen’s, which traces its history to 1859 and today operates four hospitals and dozens of smaller health care centers and labs throughout Hawaii and the Pacific, employing more than 7,000 people, acquired the shuttered St. Francis West campus in 2012 and reopened it in 2014 after spending $100 million on upgrades that included renovations and doubling emergency room capacity. Queen’s also added an eight-story parking structure a few years ago.

Now, Queen’s says it needs to do more to serve the fastest-growing area in the state, which includes the 11,750-home Ho‘opili community in an early stage of growth, the University of Hawaii-West Oahu and the still-developing resort areas of Hoakalei and Ko Olina.

“As families continue to discover the additional planned communities, shopping and work options, the population on the west side will continue to increase making access to high quality, comprehensive health care essential,” Queen’s said in its application. “Expanding the Queen’s-West campus … is essential to meet the increasing demand for access to health care when and where our patients need it.”

Queen’s said in its application that the population of Waipahu, Ewa Beach, Kapolei and Waianae is expected to increase by about 6,000 people, or 2.5%, between 2020 and 2025.

The organization is also planning a more than $200 million medical complex that includes a hospital with an emergency room at Koa Ridge between Waipio and Mililani, though this facility is envisioned to primarily serve Central Oahu communities.

Some things Queen’s intends to provide in its West Oahu campus expansion include maternity and neonatal care, which it said does not exist in Leeward Oahu despite the fact that families from that region account for 60% of Oahu births.

“Expectant moms and their partners need to travel either to Honolulu or to the windward side to give birth, which can create anxiety and pose safety issues due to traffic and timing,” Queen’s said in its application.

Another planned improvement is increased emergency department capacity. Queen’s said its West Oahu emergency department is designed to handle 120 patients a day but received an average of 180 a day prior to the coronavirus pandemic, which often resulted in diverting ambulances to other hospitals.

Other benefits from the expansion would include more pediatric care, as well as more outpatient surgical services.

More hospital rooms would allow every patient a private stay, compared with existing facilities on the property, where 40% of rooms are shared, according to Queen’s.

“Private rooms allow for a better patient experience, including more space for families, improved infection prevention and decreased noise,” the application states.

A few existing parts of Queen’s West — the Sullivan Care Center hospice facility and the original physician’s office building — would be removed under the plan.

Building heights for new buildings are proposed to range from 40 to 102 feet, compared with existing buildings of 26 to 85 feet.

If the permit is approved, Queen’s anticipates carrying out its expansion plan in four phases.

An initial phase would include one hospital tower with patient rooms next to the existing hospital building, a main lawn and removal of a surface parking lot with 562 parking spaces.

Chang said this phase, if plans proceed without difficulties, could break ground in 2023 and be done by the end of 2025.

A second phase over the following five years would mainly complete interior patient room spaces not done in the first phase.

The third and fourth phases, spanning another five years, would include a second new hospital tower with patient rooms, two new physician’s office buildings, a new outpatient building, a new parking garage with up to 820 spaces, an event lawn and removal of the original physician’s office building and the hospice center.