Construction barges and crane vessels prepare for construction work for the relocation of U.S. Marine Corps Air Station Futenma in waters off the Henoko district in Nago, Okinawa Prefecture, on Feb. 6. (Mitsuru Matsui)

NAGO, Okinawa Prefecture--The central government began initial offshore construction work in waters off the Henoko district here on Feb. 6, marking a major step to relocate U.S. Marine Corps Air Station Futenma from the prefecture’s Ginowan.

Work to drop concrete blocks that will anchor silt curtains to the Henoko seafloor for the construction commenced at 8:40 a.m. that morning, the Okinawa Defense Bureau announced.

According to the bureau, which is under the Defense Ministry, silt curtains will be deployed during underwater construction to prevent the dispersal of sediments from the ocean floor. The curtains will be secured by concrete blocks each weighing 11 to 14 tons.

These cement structures carried by two construction barges were loaded onto one of the two crane vessels at the site and prepared for deployment around 11 a.m. Once ready, 228 of the blocks will be dropped in four locations at the site of the planned facility.

It is expected to take several months for the silt curtains to be set up. Once the structures are deployed, the site will be surrounded by seawalls before construction of the new base begins. The central government hopes to finish constructing the facility in five years.

“It’s a very rough way to deal with the issue,” Okinawa Governor Takeshi Onaga said, criticizing the central government’s attitude.

Many in the local populace have been actively trying to block the construction project.

About 100 protesters clashed with riot police officers in front of U.S. Marine Corps Camp Schwab, located ashore from the site, when four dump trucks arrived shortly past 9:30 a.m.

The activists attempted to stage a sit-in to block the entry of the vehicles, but were forcibly removed by riot police officers.

Shouts of “Let us go,” and “Stop police brutality,” were heard from protestors as they were dragged away by police.

The prefectural and central governments have been locked in an ongoing standoff over the relocation project, which was initiated based on a Japan-U.S. agreement.

The relocation work originally kicked off in October 2015, but ground to a standstill after the prefectural and central governments reached a settlement in March 2016 in a series of lawsuits against each other.

As a result, construction was confined to setting up work spaces along the camp’s coast and other land-based jobs.

The central government resumed construction after a lawsuit it filed against Okinawa Prefecture last July was resolved toward the end of the year. The Supreme Court ruled that it was illegal for Onaga to nullify his predecessor’s approval on the central government's reclamation project off Henoko after rejecting his appeal on Dec. 20.

Onaga is considering a number of countermeasures against the effort, including filing a lawsuit against the central government if they continue reclamation work even after the prefecture refuses to renew a permit that allows them to destroy coral reefs. The permit is set to expire at the end of March.

“A judicial decision that ruled that Governor Onaga’s decision to nullify the approval on the reclamation project was illegal was finalized by the Supreme Court,” Chief Cabinet Secretary Yoshihide Suga said in a news conference on the morning of Feb. 6. “We will be continuing the project, as we are a state ruled by law.”

Suga stood by the position that relocating the air station to Henoko was the “only solution” in guaranteeing the safety of Futenma residents and maintaining the deterrence posed by the Japan-U.S. alliance.

Such a stance was shared between Prime Minister Shinzo Abe and U.S. Defense Secretary James Mattis in a meeting on Feb. 3 in Tokyo, according to Suga.

(This article was written by Go Katano and Shun Suzuki.)