Hawaii won’t start to get a previously announced 2,700 Marines from Okinawa, Japan, until 2027 in a move that is expected to cost $1.3 billion to $2.5 billion for infrastructure (in 2012 dollars), with training ranges a particular concern, the U.S. Government Accountability Office recently said.

The Defense Department continues to plan for the removal of some Marines from Okinawa to take pressure off the Japanese island prefecture, which has 18,000 Marines. As part of that plan, the Marine Corps wants to move 4,100 Marines to Guam, 2,700 to Hawaii and 800 to the mainland, and rotate 1,300 to Australia, the GAO said in a report released in April.

“Japan serves as the United States’ most significant forward-operating location in the Asia-Pacific region, accommodating approximately 55,000 military personnel,” GAO reported.

According to the agency, the Pentagon has taken some steps toward the relocation, including “some initial infrastructure plans” for Hawaii and Australia, but “it did not provide a reliable schedule for the Marine relocation to Guam,” and it needs to examine training constraints on Oahu.

The Defense Department should review infrastructure plans and cost estimates, the GAO said. In response, the Pentagon said it was already taking some of the recommended steps, including a “comprehensive update” of the Guam schedule.

The Pentagon also said that U.S. Pacific Command, headquartered on Oahu, “explained to the GAO that the existing plan cannot be considered fixed and final because of the requirement to continue adapting to changing conditions.”

The GAO said the relocation to Hawaii is now expected between 2027 and 2031 — after the Guam moves between 2022 and 2026.

The timeline has slipped a bit with the complexity of the changes since realignment efforts were initiated more than two decades ago. In 2013 the head of Pacific Command said the Marines’ move to Guam would be completed by 2020, and the move to Hawaii by 2026.

The GAO report also references a 2014 Naval Facilities Engineering Command Pacific study, never released to the public, that looks at the capacity to base the additional Marines on Oahu.

According to the Marine Corps and Navy evaluation, the relocating units won’t all fit on the Marine Corps base at Kaneohe Bay. But all the units could be accommodated on existing Oahu Defense Department land.

The units pegged for relocation to Hawaii include:

>> 3rd Marine Division Headquarters and Headquarters Battalion.

>> 12th Marine Regiment Headquarters and Headquarters Battery.

>> Combat Logistics Regiment 3 Headquarters and Headquarters Company.

>> 3rd Medical Battalion.

>> Marine Air Support Squadron 2.

>> Combat Assault Battalion.

>> A portion of the 21st Dental Company.

A two-star general would come to Hawaii from Okinawa with the 3rd Marine Division headquarters move, according to the study.

Areas that could accommodate all the relocating Marines include the Army’s Helemano site, the Navy’s Kalaeloa golf course and riding stables, and the Navy’s Lualualei Annex Magazine and Lualualei Annex Radio Transmitter Facility, according to the studies.

Locations that could support some of the relocating Marines include Marine Corps Base Hawaii, the Navy Marine Golf Course, the Navy’s Pearl City Peninsula, Marine Corps’ Pearl City Annex and the Navy’s West Loch Annex.

About 9,500 Marines and Navy personnel are based at Kaneohe Bay now, according to the Corps. The Okinawa relocation would add 2,700 Marines and 1,900 dependents on Oahu.

The Defense Department “has not resolved the training needs” of the 2,700 Marines proposed for movement to Oahu, the GAO said. “The addition of the Marines will likely cause additional strain on already stressed training ranges in Hawaii.”

As of April 2016 the Corps had not developed a timeline to develop training details for Oahu, stating that planning for Hawaii was not yet a priority, according to the GAO. The Marine Corps said an environmental impact study would have to be completed before the Oahu move could take place.

“However, citing a March 2014 Hawaiian islands training study, Marine Corps officials noted that installations in Hawaii lack sufficient range capabilities to fully support training of units already stationed there,” the GAO said.

Because the sites are not sufficient, about 90 percent of Marine Corps training occurs on Army ranges, the government agency reported.

“According to the March 2014 study, the limited ranges in Hawaii have historically been used at a close-to-capacity level,” the GAO said. Infrastructure planning, in turn, “takes years to complete in advance of allocating resources.”

“It is important to resolve this capability deficiency now because these training issues will become exacerbated as additional Marines begin to relocate to Hawaii,” the GAO said.